I'm with Roger on this one. This is absolutely idiotic. It is not unheard of for a couple to call off a wedding at any time. Even within weeks of the wedding. This guy is already planning on cheating on his future wife (because if he isn't willing to call off the wedding for you, why would he even consider divorcing her for you?)
You need to cut all communication with this jerk. And that is what he is being right now, a jerk. Even if he suddenly decides to cancel the wedding, why would you even consider a relationship with him based on his actions here? Run from him and run fast. You can do better.