Hi. Before I reply I just want to note that I am coming from a completely different (and possibly unhelpful) position. I am a 19yr. old female and the abuse from my parents was mostly verbal/emotional and never sexual.
I am finding as I get older I remember more things that I have repressed, but these are usual about sexual assaults which are again, not linked to my parents. I am not a huge fan of remembering them, but my brain seems to know what it can handle and what it cannot. And so it does a decent job of protecting itself.
As for whether he should tell her, that is a completely person-by-person decision. Sky is probably right about her reaction. However, if it will make your H feel better to get it all off his chest and let it out and express himself then he absolutely should. If it will just make him feel worse and he doesn't ever want to deal with her, the he shouldn't. His T will be a lot of help in making the decision and the decision may also change with time.

I know you have a lot of questions, and although we don't have all the answers, we can definitely give you some ideas based on our own experiences. I hope this might help.