So many man pleasers, it's worrying.
soscaredaboutitall. YANBU, not at all. It's perfectly natural to be pissed off that you helped him 'improve' & now he's fucked off & left you with the kids to provide for & worry about while he's out having a great time. Wanker.
However, beyond having a bit of a rant there's not much you can do about it except go through the legal channels to get what he's legally obliged to pay towards the kids. It's not much, but it's better than nothing.
Then try to stay off social media or block him. I know it's hard not to look, BUT it's only hurting you.
Write a LONG list of all the things that make him the wanker he is.
THEN write, lists, a narration, a future that makes you happy. Do little things for yourself that don't cost much but make you feel good. Do nice things with the kids - make Friday Nights fun night, play board games, watch a movie, pop popcorn...get off the hamster wheel and have fun.
Find a local teenager to babysit & go out on Saturday nights, even if it's only once a month.
See friends, invite a friend & her DC over for the weekend.
Redecorate your bedroom.
Whatever, just start living - it doesn't need to cost much, just find your happy place.