Patience your xh sounds unhinged tbh, how can he go into such a fury within seconds over a reasonable question about seeing the dc ? Actually saying that after spending almost 5 years with someone in the past who did give me black eyes I know what they can be like.
As you say maybe speaking to a solicitor in the NY will get some good advice.
I do wonder though ultimately if its going to be better in the long term if he does not see your dc. A year on and he is very hit and miss and I think not seeing them over Christmas is the pits. Its not just that you are concerned at them being in his care but that every time he says hes going to have them and doesnt is another kick in the teeth for them and as they get older they will feel it more. Maybe like either ripping off a plaster or taking it off very slowly you are better to deal with the pain of making a decision that he wont see them and going from there.
Also theres the fact that trying to organise access means enduring his nonsense and on a day when you feel vulnerable that is going to affect you and you just dont need it . Why all this time later should you have to put up with it.
I know a night out or time off at the weekend is the least you deserve but is it worth this grief for those few nuggets of freedom because as you say I dont think he will knuckle done to a routine of regular contact.
I dont know what the answer is and its so depressing the way men like him get to make the choice "Oh shall I bother seeing my dc or not" whereas we are by default responsible for them come what may.
Being positive though you have two lovely dc and all the fun things you post about them in their tiaras and Ben 10 gear - they sound like fantastic kids. They will be older and less hard work before you know it and both be at school and your freedom will gradually increase and everythings gets easier.
Remember what LC said about her dc and how they will know what you have done for them and how close you all will be. You are without doubt a big enough parent to do the job of Mum and Dad and if their Dad continues as he has been sad to say they are better off without him around.