Have you read "No More Mr. Nice Guy"? It may really help you. I know, because I AM one (a "Nice Guy.") Women don't respect "Nice Guys" (there's a difference between being a strong man, who is nice, and a "Nice Guy"), and women also tie their feelings of "respect" VERY closely with their feelings of "love."
I'd suggest you seek out three posters -- Coach, Gucci Loafer and dburt -- and get some feedback from them. I can help you with the infidelity part, and give you some ideas for affair-busting and boundary-setting, but I think that is a secondary issue for you.
