Tristan, as in all things in life, you will not be able to control every single that happens, nor should you. I think you already know that.
Let's keep things in perspective. She has resisted his attempts to see her again (like returning the book). He called, she answered. She regrets it I am sure. All it did was make her feel bad, all the way around. She doesn't WANT contact with him. It happened that time. She was open and honest with you about it, I don't know how that isn't "transparent." Or how that is second guessing your marriage. All her actions indicate moving forward with you, so I don't think saying or implying she's second guessing because of one miserable phone call is necessary. Take it one day at a time. I don't see where her attitude in this is that she MISSES him so much and is undecided and waffling. It was one call and it wasn't pleasant.
He may continue to try. It makes him look pathetic, miserable, and selfish. It will not draw her closer to him. He is ignoring her feelings.
It is counter-intuitive to ignore a harasser but that is the best tactic. That doesn't mean you are ignoring the situation, just HIM. I recommend NOT confronting him, why? Because people like that don't think the way we do. A normal person would be intimidated, a weirdo will feel justified.
Ignore/bore him into oblivion, he will find someone else to get his drama. It's hard, but effective.
Last thing, your wife doesn't need any strong arm approaches. She's shown that she will now act in good faith towards the marriage, if not perfectly. She is probably being a bit naive right now, but don't panic, and give her some space. Giving her space has only brought her closer and closer. She is also confiding in her friends right now, apparently, and they clearly think the guy is bad news. They will also continue to influence her. You have NO IDEA how persistent girlfriends will be in this arena.
Stay cool...
99% of this post is spot on (yes even I can admit that), that last part about the girlfriends, I'm sure they were in on the affair as well, encouraging it, that's the part that you can't control as well - some of them probably encouraged her moving on with her life. leave you and telling her to do better, etc. And unfortunately some of them will still have that mindset.
The only thing you can really do is give her space, ignore the OM, talk to her when she wants to talk but don't attempt to try & fix anything, be her sounding post, allow her to talk to you & open up to you and be secure with you, continue getting a life, maintain your personal life, give her the gift of missing you every now & then and make sure that those times you guys are together are really good times. Don't bad mouth the OM, all you do is give him attention and there is no such thing as bad publicity. Ignore him, you can't confront him, if you did, you & I both know your self-control would be out the window and he would need to look up a good dentist afterwards for extensive dental repairs. No jealousy, no insecurity, just keep on doing what you did to get you here because it worked. Continue being a great dad, continue being a great spouse and continue being a great YOU.
