This is Penny's philosophy.. if you aren't around, they have no one to pick on but each other.. and they WILL... So hit that safety zone and don't come out of there.. let your friend screen your phone for you
Make it clear that you want the marriage, but you need to distance yourself from his affair ...
Family members do this with alcholics too.. you walk out on them and tell them you love them... if you leave an alcoholic or any addict with nothing but their addiction they will either rise or hit rock bottom VERY FAST...
When you go to your safety zone he has no one enabling him anymore.. so stay there in my opinion...