"This side of poly is harder than anything I've ever experienced!!!! How do you do this side?????"
Well, the thing is, this doesn't seem like a poly problem to me. It's happening in a poly situation, but it's not about the usual jealousy issues, boundary issues, time issues, or any of that. By lying to this woman about something so fundamental he is deeply wounding you both. I don't wanna sound melodramatic, but this feels more like if you guys were in a BDSM relationship and he started hitting you outside of "playtime" without your consent. Sure, it seems like there's a connection, but he's being abusive, at least emotionally. This is a pretty warped form of poly.
I really feel for both you and this poor woman. He'd better come to his senses quick and realize how awful he's being... then beg forgiveness from you both. No amount of attitude issues on your part justifies him pretending to a new lover that she is going to be someone special in his life, while telling you the opposite. It makes me so sad just to think about it. Obviously he's lying to someone, and if he doesn't shape up he may well end up with no one.
I'm sorry to hear about how much this is hurting you. I can understand why you'd want to self-medicate, but pleeeeease be smarter than that.
An aside... I'm surprised to hear that Butch and you don't even exchange little gifts. Obviously everyone's poly is different, but if you guys have a loving connection that involves dates and physical affection, how would little signs of affection tip things over into a problematic territory?