Ok, I've been reading this thread from the beginning. Your ex says that he is wrong, sorry, blah blah blah, but he won't tell you about what exactly was going on? If you're in the wrong , as he definitely was, you either need to be 100% humble and take whatever kicks in the nuts may come, or be a 100% jerk, deny everything and move on. He's trying to play a middle ground, and there isn't one. I also don't know why, if he's been gone for months, why it will make any difference whatsoever if you know the sordid details of the affair. When you first found out I would totally understand, but now after so much time and his departure the details are moot. At this point he owes you as much as you owe him, which is nothing.
Do yourself a favor and don't get back with this guy. Some cheaters actually change, but the overwhelming majority do not. Get started on those divorce papers.