A) Husband moves back. Does that mean he definitely, for certain, is not having an affair.
B) "Prove" the affair is over. Will you believe it? Won't you still wonder sometimes or be suspicious? How long is that proof good for? How do you know another affair won't start up?
C) Stop caring. That may not entirely be possible. For example, you might "care," and it might hurt to think it is happening or could happen again. A more realistic approach might be to work towards being stronger, accept what is and do the best with that. Works towards being the kind of person no one would want to risk losing... and if they are stupid enough to do that then accept their stupidity and weakness and stay because there is reason enough to do so, or leave because there is even more good reason to do so. And be content and emotionally secure (no anger, no blame, only good will) with whichever decision you make.
D) Decide you don't want to deal with it anymore and divorce. Get used having your daughter gone either half the time or every other weekend. Get used to her being with either a series of OW or a new step mom or two. Get used to being verbally bashed (either to your face or behind your back) by ex-husband and new girlfriends or wives, meet a new guy, date or marry him, and then learn he has "something else going on"... etc...
There is no arriving, ever. It is all a continual becoming.
