Oh humpty 
I remember you from another thread and you were so positive and inspirational. Don't let him drag you down.
The biggest favour I ever did myself after leaving XP was to realise that hell would freeze over before he ever even recognised that he had behaved badly. I will never receive an apology from him and he will never change. These are cold hard facts that I have as much control over as night becoming day. It sounds obvious but it's actually quite hard to really, truly, understand. Once you do, it all becomes a lot easier, I promise.
The day I decided my X was a lost cause my life became easier. I am not obstructive but I have laid down my (reasonable) ground rules and refuse to enter into any discussion about them. I spent a couple of years trying to be the mature, reasonable one who acted in the best interests of her children even if that was in conflict with what was best for me. But the truth is my XP is selfish, unreasonable and abusive. You cannot talk to him without him either walking away or becoming violent.
In the end, I realised that by fighting so hard for contact to continue between him and DC was actually counterproductive. All I was doing was creating a situation where I was setting my DC up for a bigger fall. Far better for him to exceed low expectations than to fail to live up to unrealistic ones. Ultimately, his relationship with them is his relationship with them so what on earth was I doing trying to organise it?! My participation should begin and end with ensuring that my children come to no harm while with him.
In the end, I sent him a witnessed and signed for letter (as a cheaper alternative to using a solicitor) dictating my ground rules. I said he could have as much contact as he wanted as long as he organised it at an appropriate venue under appropriate supervision - friends were not acceptable (which in reality leaves only a contact centre). Unless it was to discuss contact I would have no discussions with him over any other issues.
I haven't pursued maintenance because in my case it isn't worth it. He alternates between unemployment and self-employment, and the amount of time and emotional investment I would spend trying to get the CSA to do their job, with no guarantee of any actual money at the end of it, is simply not worth it. However, if he held down a steady PAYE-type job, I would involve the CSA as he chose to have these children and does not get to abdicate responsibility simply because he cannot be arsed.
In short, work on trying to accept that your X is what he is. Don't obstruct contact unless there is good reason, but don't try to set it up either. Leave it to your X to do the running. If he doesn't, he doesn't. Ironically, since I have been this tough, my X is a lot better and we can actually get along quite well now if we ever find ourselves in the same room. He is still shit at arranging contact but he does at least stick to any arrangements he makes and he treats me with respect (even if my name is mud out of earshot 
)
Sorry you're feeling so though. You're worth more than this.