First of all welcome to PC!

I think it might help to try and think of things from his point of view. You know he has already been mistreated/betrayed once by his ex who continues to be manipulative to the family. So obviously, it's going to be hard to trust anyone again. He probably sees this bump in the road as a downturn to the relationship as a whole. I know that if my boyfriend and I fight I can't help but have flashes of thought that this is eventually going to turn into my past relationships. But then I realize that, when others would get out of hand, the guys never wanted to work it out. But my current boyfriend wants to work through it and that's the difference.

All relationships go through hell. They go through some unimaginable pressure, temptation, hardships and everything else. The thing isn't to look at how bad it gets, it's whether you are both ready to stick with it. Maybe if you make him realize that even when things get bad, you are willing to stick through it, he might realize that not all relationships are going to turn out like his last one.

If all else fails you need to think about whether it's the wedding or him. I know a lot of people that got married just for the wedding and the experience - not because of the guy. I definitely would not go so far as to say, if we aren't going to talk about the wedding we might as well not talk at all. I'm wondering why you "need" marriage? That just puts more strain on the situation. You need to get at the bottom of why he is getting cold feet or get to the bottom of why this relationship is not enough without the ring.