If you can see all the reasons why he broke, then try (it's hard) to adopt a Mother Theresa attitude about him. Stick to the high road, take care of business as needed so that you and your kids are ok, but try to cultivate a kind attitude towards him.
I struggle with this to this day, even though my ex and I split 7 years ago. he had multiple concussions which didn't change who he was, but definitely brought the bad parts more to the fore. Mostly now I feel sorry for him, but when he's being particularly selfish or evil towards our adult kids, I can really get irate about him. That happened this last week and it just so happened I was reading a book about vibrations, and it made me acutely aware how much damage it was doing to ME, letting my vibrations get upset by his pettiness. So I'm working again on cultivating a more Buddhist perspective and not letting him get to me, and even trying to cultivate some compassion for this lost guy.
