I think it would be really, really easy to try to fill up the hole this crisis has caused with the kind of excitement that comes with dating and meeting new people
Read this again ^^^^
If your suspicious are right. He is filling up the hole that this crises left. He is escaping the sheer 'weight' of his responsibilities and the guilt he feels when he looks at you and replacing it with someone who doesn't represent the same baggage. OW do not matter are a distraction and will not last. He is not in a fit state to make a relationship work with anyone. He has not done the work on fixing himself yet. Until he does, every attempt at a meaningful adult relationship will fail.
However, nothing I say will stop you from hurting right now. Your H is being a selfish [censored]. Pound your hands and scream into your pillow. Call your sister and rant. Do what you have to do to get yourself through this. Remember, I am shred every pre kid photo in the house the day I found out H was dating. I confronted OW then and there and called her an ugly fat version of me (that was one of the nicer things I said). Then I woke up two days later, wiped away the tears and apologised to him (which I still think was the right thing to do) and then threw myself at him (which in hindsight was a mistake). I did not apologies to her because, well, because I will poke burning hot coals into my eyes before I apologies to her.
