I can only speak for myself in that I am definitely rooting for you!
I just think (and I've said a few times, and so did nycindie) that you need to lay it out on the table with Sundance so it's out in the open and clear that the lying/trust thing is now a HUGE issue that needs to be dealt with now-- not later when it's too late and no matter what he says you never believe him again.
I am hoping that hearing you lay that out to him, how damaging his lying is to your relationship, maybe that will kick him in the ass enough to pull his head out of it.
I know that sometimes it takes realizing you're about to fuck up your relationship to get you to really deal with things. Maybe right now he's so caught up in whatever he's doing he's not really SEEING that. I know it seems obvious, but sometimes people just don't get it when they're screwing things up until it's too late, and my thought is that you need to point it out to him BEFORE that point.
Now, whether he steps up or begins a conversation about it, that's up to him. But at least you'll then know that you were clear with him, and you'll know where you two stand (right now). I'd just hate to see it get to the point where by the time he figures things out, the marraige is too broken to fix. I see that a lot, especially when the hard conversations didn't happen until the people were done emotionally.