>>1 you can't change the past and sometimes it gets hard, but moving on is really important. However, he didn't really give you the chance to move on, which isn't fair at all. Think of it this way, he could have done something really awful to you if you would have stayed with him, it's a good thing that you left him when you did. You weren't wrong to leave him after cheating, you also didn't mean to cheat, you did the right thing and told him the truth, he was the one who couldn't move on properly.
The guilt may always be there, just like a lot of emotions are, but just try to ignore it and tell yourself that you are a wonderful person, that you're moving on, and that you've learned from your mistakes. I hope this helps ^.^