Rollar Coasters are no longer fun

[Dom R]

That wasn't it trust me. He went to the mountains with her right after that. He was telling her goodbye because she dumped him but then she took him right back. It was his way of looking pathetic and getting her back. Two days later we slept together again and then 4 days later they went to the mountains together. Wow I have no self respect. I really am pathetic when I really type that out.

you are not the pathetic one. he is.
you are doing an incredibly tough thing.

I've read that when there is an OW involved, it isnt uncommon for the H to yo-yo back and forth trying to give her up.
Just like multiple failed attempts to give up smoking.
Even HE knows this. He referenced "withdrawal" in his email to her. Sounds like he's actually read some marriage recovery books.

Anyway, at least he called me, he was upbeat and for the first time in weeks he was nice to me. I mean really really nice. We will see.

Attagirl. You're understandably tired. So, how about letting him do the work? If he's nice to you, then keep talking with him, and at some level (even if it's only at the "politeness" level) show some kind of positive back in return.
Otherwise, just keep it about the kids.

aka, "Keep doing what you are doing"
I think you're doing good things. Even if, ironically, that actually mostly means, "do nothing"