I also wondered about this, actually. I think we're different in that I was slightly afraid to lay it out because I was fearful of a negative answer.
But, then I grew a pair, and laid it out. On Friday, if she doesn't give me dissolution paperwork, or confirm she has ended her affair, I file divorce. I feel completely clear because she knows exactly what she's walking into.
Knowing what I know of you - I think that you should lay it out. You are a "nice guy" - and I believe it will ease your conscience - regardless whether you should have to or not.
I also remember in the early days with W - asking her what the heck she WANTED, and she would sniff and say, "Well, if you don't know, then it doesn't matter."
ARRHGHGHGHGHGHGH! Again, I don't know your xBF, and I don't know if he even deserves another chance, so I'm speaking from a neutral man standpoint.
