Girafe - I just want to tell you that I am in a similar situation as you are! Do you feel as though you were conned by your other half? Like he painted this picture of sunshine and daisies and you fell for it?
I have been married for a year and a half to a guy that I'd been friends with for almost 10 years. We seemed to have the same beliefs about marriage and child rearing. Unfortunately, it was all a lie.
His now 11 year old son lives with us - he's had custody since the boy was 4 when his mother walked out and left him on the porch begging her not to go and promising to behave (poor kid!!). Unfortunately, his father is really not that great a custodial parent. The boy has behavioral issues that were SO bad at one point in time he was thrown out of the only school in the area and forced to go to a school about 30 miles away. He's been labeled 'Behaviorally Challenged', and is actually back in the local school. As I am a stay-at-home mom and wife (was permanently injured in a car accident 3 years ago and can't work), I've been taking care of the boy's educational needs AND taking care of him in general because his father (my husband) works really awful hours and spends evenings asleep on the couch. Not to mention he'd told me before I moved down here when we got married that he was glad I was getting involved in his son's life because he needed a mother figure.
To make a long story short, between the boy's defiant attitude and behavior issues and his mother's awful attitude towards me (she tried hitting me with her car and has openly threatened me in court), I have a VERY difficult time trying to straighten the boy out. He's allowed (against counselor's orders) to play M-rated video games that portray violence (the counselor said these contribute to his aggressive and nasty demeanor) and watch TV all the time. As a result, he developed chronic stomach aches, days of endless vomiting, difficulty breathing and bouts of diarrhea. I took him to the doctor and was told that he was impacted with feces; an x-ray showed his entire large intestine was full of feces. I was given instructions on how to take care of it, and the boy was told TO HIS FACE that he's only allowed 2 hours of video games and/or TV each day and MUST get AT LEAST one hour of exercise each day...as well as refrain from certain foods and drinks (like 5 cans of soda a day and a constant stream of Slim Jims and assorted candy every day). Well, I tried to do what I could to abide by the doctor's orders but everything I did was met with opposition by the boy. His father was no help and, in fact, made it more difficult for me to get the boy to do anything I asked of him by taking his side RIGHT IN FRONT of the boy! These are some of the things I was told by my husband regarding what I was trying to do with his son:
1. I'm too extreme with discipline because I would take TV and video games away for the night if he lied about homework or misbehaved in school and we were notified of it via letter or phone call. (What? I should pat him on the head and tell him he can do better and send him on his merry way?! Not if we're getting 3 notes a week sent home and 2-3 calls a month about his behavior!!!)
2. The school has labeled his son and they're singling him out when he's bad. Aside from one or two incidences where his teacher at the time WAS being a little harsh, everything the boy did was a direct violation of the school's Code of Conduct that the students were given at the beginning of the school year and was reviewed with them in school as well as at home. But in my husband's eyes, his son was a perfect angel and the school was out to get him.
3. The doctor tells EVERYONE to get an hour of exercise every day! Okay....before we got married and were just friends that commiserated on the hell our exes had put us through (I have a son that's a little under 2 years older than his youngest - the child from Hell I'm talking about), he told me that he fed the boy an almost constant stream of fast food because of their schedules. He said it remorsefully and told me he WANTED his son to eat better but just never had the time between working full time and trying to raise the boy and his three older siblings by himself (he had 3 teens from a previous relationship and had full custody of them as well). But now that I'm here, I'm not allowed to make the boy get any exercise or eat better than he was. Yet the boy's BMI was 23 at the time (2 points below being medically termed 'obese' by the AMA) and almost 20 pounds overweight for a (at the time)10 year old boy that is only 4'0" tall.
No matter WHAT I do, I'm constantly told that I'M wrong and that there's nothing wrong with his son. Yet the boy constantly gives me dark looks (he squints his eyes at me and puckers up his mouth like he's trying to intimidate me) whenever I ask him to pick up his room or put his toys away, take a shower, brush his teeth, etc. He was allowed to take his socks off and shove them into the couch cushions or just leave them on the floor or in his bed. He is allowed to walk around the house in just a pair of boxers. He was allowed to eat and drink in his room until I put an end to it after opening his door to get him up for school one morning and getting assaulted by a really nasty odor...only to find a 2 week old pitch black banana peel in his waste basket that he craftily wedged under his bed and now had a cloud of fruit flies hovering around and a line of sugar ants marching into. And STILL I'm the bad guy.
His son has kicked, punched, strangled and thrown things at my son whose only crime was beating his son at some video game or another. My son chose to stay in our hometown when I married and moved 4 hours away, so I see him for holidays, school breaks and the month of August each year. Both of the Augusts my son came to stay with us he wound up going back with his father early because of my stepson. He didn't want to talk to me for a while after this past August because he was upset that things were as bad as they are here with his stepbrother.
Right now my stepson had daily chores (so he's physically active every day instead of laying on his bed like a little beached whale) and isn't allowed to watch TV until 7:00 pm. He is forced to go outside and play after homework and chores while dinner is being made. There is a set of House Rules that are strictly enforced.
And some of the rules are so STUPID!!! I had to actually make it a rule that he minds his own business when adults are talking because he CONSTANTLY interrupted conversations between my husband and I, and would come out of his room any time the phone rang and sit there listening to the conversation THEN QUESTIONING HIS FATHER AS TO WHOM HE WAS TALKING TO AND WHY HE WAS TALKING ABOUT CERTAIN THINGS!!! And this is a child who is at an age where he tells his mother EVERYTHING (even if it isn't her business) and she tries to turn around and use it against my husband in court (never worked though LOL because she's a total moron).
Another rule is about hygiene because this is a child that didn't bother to wipe his butt after taking a crap and would somehow manage to have poop (NOT just a stain, an actual clump of poop!) in his BOXERS! I had to have his father go in and show him in the shower how to wash his butt. His father's excuse as to why he didn't just do it before? He's embarrassed to touch himself like that. But we're not embarrassed walking around smelling like crap INCLUDING OUR BREATH because we have our hand up in our butt crack, then suck on all four of our fingers? Yeesh! Oh, and did I mention how the child doesn't retain anything?! I told him countless times to flush the toilet after using it, and actually had to go so far as to hang a big sign above the toilet to remind him to flush it EVERY TIME he used it!!!
I have a note on his wall by his door reminding him to shut off his TV, lights and/or radio whenever he leaves his room to go someplace or eat supper, take a shower, etc. I still have to remind him despite the sign.
This is a child that's never actually told me he hates me or said he doesn't have to listen to me, but shows me in his daily actions that he resents my coming in and actually trying to make a decent human being out of him because I don't believe that parents should wait on their children...which my husband did. He'd make up a plate for dinner and rather than have the little brat come out to eat, he'd actually take it into his room and serve him while he played video games, then bring his plates and stuff out for him when he was done! Any time he was told to pick up his room, he'd ask his father to help him and his father would go pick up his room for him while he sat on his bed playing video games! I put the kibosh on ALL of that - he eats out with us, puts his dishes in the sink when he's done, and he also is expected to keep his room clean EVERY DAY.
The room cleaning was a nightmare. His counselor told us to hangup a sign in his room about "What Makes A Clean Room" and lists 3-5 things that he needs to do in order for his room to be considered 'clean'. So he has to have clothes either put away if they're clean or in his hamper if they're dirty (he has a sign on his hamper explaining what clean clothes are because he'd come back from his mother's and just dump his bag of clothes in the hamper and I'd find folded socks, boxers and shirts in his hamper buried in dirty clothes (last weekend he never changed his boxers!). Anyway, it's the usual list - clothes and toys picked up, no garbage on the floor, etc. He fought me SO BAD on it that I finally issued an ultimatum. Either he picks up his room the way he knows he's supposed to the first time I ask him (I'd been asking him 4 or 5 times to do it and get nothing but dirty looks or a lazy kicking of crap around on the floor attitude), or I come in and clean it myself. And MY cleaning his room means ANYTHING that isn't put away like it should be according to his Clean Room rules gets thrown in the garbage. I don't care if it's a $50 video game or a stuffed animal his mother bought him as the latest in her bribery attempts to win him over so she can get custody. So far, his room gets cleaned the right way the first time I tell him to pick it up!
The biggest hurdle, Girafe, is exactly like yours - the father NOT agreeing with you or defending you to the kids OR his ex. All I can tell you is that you need to stand up to him. Issue a few ultimatums about either dealing with his unruly children or getting them some counseling (we tried that but the counselor was a total weirdo and my husband harped on everything I was told I was doing wrong but conveniently blocked out anything he was told HE was doing wrong). Walk out if you have to. Start standing up to his kids. If the one hits you, call the police and report it - have the child arrested once or twice and they'll learn not to hit you anymore. If the 16 year old wants you to chauffer her someplace, make her earn it. Either she does chores around the house or she'll have to find another way to get wherever she wants to go. With the 16 year old it's tough because at 16 they're able to get away with more. The 13 year old though....you can beat him/her at his/her own game! I did that with MY son once - he threw things at me and threatened me so I called a friend of mine that was a police officer at the time and he came out and mock arrested him He thought it was cool at first, then once they car pulled away and my friend explained what was going to happen from there, he changed his tune 
If your spouse doesn't stand behind you and lets his kids get away with things he KNOWS they shouldn't...take matters into your own hands. BE the parent the kids need and if it doesn't get you anywhere, WALK OUT.
I'm at the point now where I will be walking out on my husband (he told me he feels sorry for his son because so many women have walked out on him...I told him if he treated the women better and expected better behavior from his son they wouldn't have walked out) if his son's behavior isn't controlled. We're making progress, but it's a tough and long road.
Hang in there and don't be afraid to stand up for yourself!
