Thank you everyone for posting. Hearing views from people who aren't emotionally involved is really helping. As with most cases, there is a lot more to this but my op would be pages long if I put it all in. I can't name check as I'm using my phone but I will try to answer some of the points raised.
When we were together, I didn't recognise his behaviour as abusive until after I left. My main reason for leaving was his serial adultery. Having read around the subject, I believe he is a classic 'King of the castle' abuser. He expected me to do everything around the house and for the DC whilst regularly screaming and shouting at me for not keeping the house in a perfect state or having his meals ready for him when he got back from work. He would often move the bar so I could never achieve his impossible goals. He had this belief that taking care of a baby and toddler all day was easy despite never wanting to help. He was also financially abusive. I was a SAHM for the first few years (until DD1 started school) but was expected to provide everything they needed plus pay several of the household bills with our meagre tax credits. I left with a lot of debt. He, on the other hand, was out drinking with his friends almost every weekend. Nothing changed after I got a part time job. He was occasionally physically abusive, one time he wrestled my car keys from my hands in front of the children and physically threw me out of the front door onto the street, refusing to let me back in, because he didn't have a car at that point and wanted to use mine. I needed it to go to work.
I have tried every approach I can think of to get him to be a better parent. I've sent emails and texts explaining why the DC feel as they do, made many suggestions on things he can do to encourage them to go, I've threatened to stop contact unless things improve, I've messaged his sister (who says she is sympathetic but unable to reason with him - her line is often 'you know what he's like), I've suggested family counselling, I've shouted back, been very blunt with him. Nothing seems to get through to him. His solution to all of this is for me to be stricter and force them to go every time. The only thing I haven't done yet is to stop contact completely but this is the position I now find myself in - deciding if or when it's time to pull the plug permanently on contact and leave it to him to seek a court order. I have cut contact down significantly since our initial separation as he was having them almost half the week over night although he would pick them up around bedtime and drop them back incredibly early so there was little value to the girls in doing this and I think they found it difficult living between two houses in this way.
The truth is, I don't really trust him to look after the girls to an acceptable standard and have wanted to cut contact on many occasions, usually after a flash point. One such time was after several weeks of low level neglect (not bathing them all weekend, not brushing their teeth) he returned our youngest wearing a top that absolutely stunk of urine. My eldest told me that he had no clean clothes to put on our youngest and so fished something out of the dirty laundry. It was very upsetting as he'd taken her out (he was better at taking them places at this point) dressed like that and the smell was incredibly strong, there's no way other people wouldn't have been able to smell her. Whenever something like this happens, I will message him (we can't talk on the phone without arguing) saying that this is unacceptable and I insist that he never allows it to happen again or I will have to reexamine the contact agreement but he is always very defensive and will level false or exaggerated complaints against me in return. This is an example from this week: For her birthday this year, XH bought DD(8) a laptop. She was in the bath one evening and asked me what porn is. I asked her where she had heard that word and she said that she'd seen the words 'free porn' on the previous search terms on the Google home page on her laptop. I messaged him to say that if he is using her laptop, could he remember to delete the history as she'd seen this. His response was that she hadn't used the computer for 'ages' so it wasn't true and returned the accusation that I sleep all the time and leave the DC unsupervised so I am 'no parent of the year'. As I mentioned, I have a chronic condition that leaves me exhausted every day and sometimes I will nap on the sofa whilst the DC watch tv or play in the same room. It makes it difficult because there's a grain of truth in what he's saying but it's not the full picture and there's no allowances for the fact that I'm actually quite ill but doing my best. Then I think, maybe he has a point - after all it's not ideal for me to be doing that so do I have any room to admonish him when I am not a perfect parent either?
The other relevant issue is that I am having some issues with my eldest DD. A couple of years ago she started having some emotional problems whereby she would have extreme tantrums (knocking holes in walls, cracking doors) or get extremely upset, talking about wanting to commit suicide, nobody likes or loves her etc. At one time I found her in her room with a belt tightened around her neck. I have been to the doctors twice about this and been referred to CAHMS but they refused to help on both occasions. The school won't help as she is well behaved there and doing well. I spoke to a psychologist at Young Minds and she recommended family therapy with XH but he refused. We had her in counselling briefly which XH paid for but after we missed an appointment due to illness, he refused to pay and DD decided she didn't want to go any more. She is also incredibly unkind and violent towards her younger sister (I'd class it as bullying) and I've noticed that she seems to do this more when they've been to their dad's. She has improved slightly recently but still displays this behaviour. This morning she told me she was going to kill herself if she had to go to her dad's this weekend but I never know how seriously to take her as she says it a lot when she's upset. I'm starting to suspect she has some sensory processing issues as a couple of friends with experience in this field have told me her behaviour fits with this. On the other hand, I wonder if this is her reaction to the difficulties between me and her father or maybe even a reaction to the way he treats her. The problem is, I have no way to tell and despite trying, can't get any professionals to listen to me or help us.
When we separated, I initially sought legal advice but was given incorrect advice which I acted upon. The upshot is that I left without any of the marital assets (he still lives in our large family home and I'm in a small private rental) and did a DIY divorce without any financial orders. I actually let him divorce me on the basis of my adultery (I met current BF a year after I left) just for an easy life. It wasn't until I sought legal advice from a different solicitor that I discovered I still had a claim to the marital assets. The letter from my solicitor was asking XH to attend mediation as a first step to a financial order. I would like to resolve contact in this too but he never responds. If he refuses to attend mediation, my only option is to go to court but I don't have the money. I am considering self representing but as I'm currently unemployed and he's no longer paying maintenance (case opened with cms but months later, they still haven't managed to get any payments) I don't even have the money for court fees. Truth be told, the only reason we're not yet using food banks is because of my parents' generosity. He knows this, but still refuses to pay anything. When I do finally get round to sorting this properly, I think I will insist on him attending a parenting course so thank you to the pp who suggested that.
Apologies, this has ended up an essay on my life even though there's still a whole lot more to it. I just feel like I'm in an impossible situation and ill equipped to fight him on this. I do believe he will take me to court if I stop contact and whilst I'm not opposed to that in theory, I just don't know how I will afford to defend a case without financial or emotional resources. I so want to get this right for my DC, but I don't know what to do for the best .