1) I haven't exactly been through the same thing, but I've lost friends over my (lack of) religious beliefs, and I lost someone very close to me because his new girlfriend couldn't handle me being in his life at all, even though he and I had already ended our physical relationship when he started dating her. It sucks and it hurts, but you can't change people. If they can't accept you there's really nothing you can do.
2) How much of a break did you and your ex take before working on being friends? If you still IM every day, it might be time to take a break to get ALL the way over him, so that you can be "just friends" without it hurting you.