Seriously- time for triage. Daughter transitioning to school and womanhood is going to be the pits, so gird yourself for that. (Have you talked to her school guidance counselor by any chance? I actually stopped in to the HS yesterday and filled them in on our current situation. D finding out about OW was a pretty big bomb for a 15 year old, so I want them to keep an eye on her there...)
You, as always, need to take care of you.
H has got to figure out how to have the kids at his house. He's a big boy who has made some big boy decisions. You don't have to help with that. Kids can complain, but I would steer them right back to daddy. "You need to talk to your dad about that..."