Rab-Have you read any of the DB books? If not go get them and read them. As far as the D goes, don't do it. If he wants it let him do it. You are doing his dirty worka nd relieving his guilt. If you file, he can tell people that you filed and booted him out.
When you read the books, you will get all kinds of techniques to help YOU and by helping yourself, you can help your marriage.
You will learn in the books that you have to Get a Life (GAL), make yourself attractive to him and let him make the decision to cut the OW loose. You cannot control his actions or his decisions. He is making bad decisons, and only he can correct it.
Good luck and God be with you.
Me: 44 S: 17 and 7 Final-6-13-08 I once went to a psychic who told me I would soon feel cheated......