I disagree with the advice to spy on your husband. That just demeans you. While I might make an exception if you're looking for proof when you're getting a divorce, the thing it all comes down to is, Do you, and Can you, trust him? If you don't, it doesn't matter if he cheated or not. You shouldn't be with someone you don't trust; if you didn't know he'd cheated on you, I'd suggest counseling to deal with your trust issues. In this case, you know he did cheat, at least emotionally, and planned to do it physically.

You and he have to decide, do you want to try to repair and save the marriage? This would mean that he needs to break off with this woman--no, he cannot be friends with her. You have the right to not have this woman in your life. If he won't give her up, IMO, he isn't worth keeping if you will always have to have his cheating in the back of your mind. If you're important to him, he will do what he has to help you build your trust back up, if it can be. I'd highly suggest counseling if you're going to attempt to keep your marriage together.

And don't let him tell you when to get over it. It may take years, and it's not up to him to decide what timeline is fair! Again, a marriage counselor can help you work through this.