Let me add to what lwb has said. You are walking in the middle of the road. Either you follow DBing, or you do what chocolateeyes suggests (hard-line it). But you are doing neither. And this is the best way to push him away.
Either follow DBing by-the-book (with a sincere effort), or put your foot down, tell him you will not tolerate his infidelity and tell to take a hike.
