Pardon if someone has already said this, OP.
I feel you are in a good position if only because this incident revealed something about you and your BF. This actually reveals that he is still very stuck in mono-mindset, or "the pattern of behavior that monogamous people have". In mono-world, it is not okay to talk to your partner about what he was considering doing. In poly-land it is normal.
In my opinion, the only option I see for you is for you both to try to gravitate more toward the "poly" way of thinking where it is normal to talk, even gush to your partner about a date or a hook up.
In my opinion, the only option I see for you is for you both to try to gravitate more toward the "poly" way of thinking where it is normal to talk, even gush to your partner about a date or a hook up.
The OP really rubs me the wrong way and comes off as selfish and very abrasive it would be the last kind of person I would ever want to have as a metamour. She seems to be very blasé about other peoples feelings other than her own. She destroyed her marriage because she wanted poly and probably shoved it down her husband's throat. Her boyfriend's marriage came apart . And now their own relationship is falling to pieces. This is what happens when the feelings of other people are not taken into account because you are too wrapped up into yourself. Good luck trying to find someone to be mono with. Selfishness doesn't work in those relationships either. I guess one of the things that should be asked of your boyfriend is if he felt that his marriage ended for you or for his freedom to have the relationships he wishes to have. If he feels it was more for you then he should consider going back into monogamy. If he feels that it had more to do with his freedom then he should certainly not give up poly for you.