I agree with the others. You cannot fix him or his mess. Unless there are consequences, then he will keep on doing these destructive things. Letting him experience consequences is good.
As for D15. As the others say, you can take the high road and not badmouth H. She is no fool and can figure most everything out. She needs to feel the anger and process her hurt and broken heart. Give her your support and give her space to do it.
Father and daughter need to go through this themselves. Try not to get caught in the middle, it's no fun. If he wants to come over and sit with her and face the music, I think it's terrific. At least he is doing a little something.
He is in a very self-absorbed place at the moment. He sees D15's rejection of him as illogical. He can't understand it. So let D15 explain it to him. You don't have to say a thing. Let them communicate. The best thing to happen is for them to start communicating again, even if it's a confrontation. It needs to happen sooner or later so might as well be now. D15 holding it in is not good for her. She has a right to his explanations. She has a right to know why she was rejected as well. Because that is how she sees it. Your H doesn't understand that. He thinks he's just rejecting you. Not the family. She needs to tell him so he can understand the FULL implications of his actions and decisions. Until he suffers some consequences, he won't reconsider his actions.
I am sorry that you have to see your kids go through so much pain, Hope. It's not fair to them and so unnecessary. But I know you are a good Mom and doing your best. You can't control their actions (Daughters' and H's). Just have patience with everyone, that is all you can do.
Me:39 H:40 S:9 D:7 First Bomb ONS:June 07 Second Bomb OW: March 08 Separated: March 08 M:15 yrs T:18 yrs H deep into A with OW Achieved ACCEPTANCE May 30, 09