Give it time, he thinks he is on top of the world right now but when he has to start paying child support and such he will think twice about how his life really is. While he is away he has no responsibilities and thinks that is the life of a king. This OW will get tired of things and she will finally boot him out. Then you can have the last word when he comes crawling back to you. Let him go out and live his life the way he wants. You can't stop him from doing as he wants but you can control your own destiny.
Do you really want someone like him right now? NO. I am not saying he won't think things through and grow up but until he does, you don't need him. Let him spread his wings, sooner or later he will have them clipped.
