Hi Dazed, I had hundreds of emails to read, too, lots of intimate descriptions of what they'd done together that they described as their "novel" - she said she was keeping the emails to read when they were old and remember all the crazy things they had got up to when they were young. In my case it was clear from the emails that they had used the hotel rooms. They also went on holiday together a few times ... in your position I'd now just assume that they (and others) did every possible shitty thing they could together and be done with it. Get checked out for STIs and send her the bill.
The cheater has to persuade the affair partner that they don't have a proper marriage (that they are "forced" to cheat through "desperation" or whatever), so your wife has likely told him stuff (lies/exaggeration) about you that fit with her calling you a twat. It doesn't mean you're a twat, or anything really except that she is trying to justify her crap.
Whatever you might have done wrong in the marriage that does not justify cheating. If she had a problem with you, there are plenty of decent ways to deal with that.
I also can't really see the point in trying to get past this. You just have one life, why not spend it with people you like? Friends, family, yourself, a new partner eventually. I'm two years on, and now just about able to be friendly with my husband, as we have split up and I have little to do with him. My children are older (youngest was 14 at the time); I'd say the time leading up to the split was the worst point for them. Immediately after the split there was relief, and since then it's gradually got better.
It is horrible at first, when all your expectations for your life are suddenly pulled away from beneath your feet, but you do get used to the new situation. I don't like the way it happened, but I now see the split as a good thing. It's given me a new chance to be myself.