You may not have any choice but to litigate just to protect yourself and the kids. They are so selfish, even going as far as not doing right by their children. Obvious that there's a reason he doesn't want to disclose his financials. Him crying 'poor me' is a bunch of crap. He knows what he should be paying and he's scared you'll do something legal and he'll have no choice.
Remember that if/when he wakes up he will understand why you had to do the things that you did. If he doesn't wake up, well then at least you got what you needed to help raise the kids.
