If he's trying to go NC, she's the issue, not him. Yes, it will be awful to lose her. But will it be as awful as watching her pick fights with you so she has an excuse to chase him? Someone who doesn't even seem to want her at this point?
If you don't decide to stand up for yourself and your M, even at the risk of losing it, you might end up feeling like the consolation prize if she finally does commit to the M.