Hi overcome, just started to read your sitch and I'm sorry to find you on here. I don't know where you are but check with a solicitor.
Is the mortgage both in your name? If it's then by law he had to pay for half of it! If he doesn't pay for the bills, he has to at least pay child maintenance! If he tries not too he won't stand a chance in court! Another thing is that if his name is on mortgage, you can't change the locks! This is what the law says as I'm based in the UK, I don't know about where you are, but worse checking.
I only know too well how you are feeling right now. Keep focusing on your kids as at the moment you are their ROCK and TBH the only grounded parents.
