"I really never thought of setting a boundary for something that I had no control over or might not even know if he crosses."
We have no control over anything they do, only our response to it.
True, if he's flaunting OW around town and you don't know about it, you can't apply your consequence. That's ok. But what about all the times you do know about it? Like when they wave to you, or D or friends see them and report back to you?
I'd be inclined to refuse all contact for X period of time after learning he crossed this boundary. "Sorry, we can talk or meet up tomorrow" (or whatever time period works for you)
He won't like it at first, but I'll bet he'll begin to respect you more in time. He seriously doesn't want to lose you. (and I don't blame him!) Now you have to stop baking him cakes.
No infractions? Good! You're best buddies. Reward positive behavior.
M: A really long time. Crisis: 5 years. She's still worth it.
Life is never made unbearable by circumstances, but only by lack of meaning and purpose. -Viktor Frankl
