Welcome to the boards.
It sounds to me that your marriage is broken and not likely to be fixable. Your wife isn't expanding her life by adding a boyfriend--she's replacing you by having a boyfriend. That her boyfriend is married and cheating on his wife means she can't run off with him and simply leave you, so it appears she's wanting to use you for basic support until she can support herself (or she thinks thel boyfriend will leave his wife).
You can try counseling. The whole "hands off" thing suggests that won't do much good, though. If it were me, I'd visit my attorney and file for divorce.