If he hates you, so what? I mean, it is a sad thing, and something that we as people hope others don't get caught up in, but that is HIS CHOICE. How he feels about you is his business - you don't have to worry about it anymore. Does his hating you mean anything about who you are, who you want to become? No; if anything, it might be a glimmer of a reflection of who you were then, when you were with him - let it go so you can grow past that and change what you don't like.
Trying to "soften the blow" in any way will just leave open doubts, fears, etc., for him, which is only playing MORE games. Tell him you need to heal and grow more, and are really considering the counseling that he suggested, but that you have to end this for both of your sakes.
It sounds like you've accepted your part in this (and it is only one part, remember - he went along with a lot of it, and didn't have to). Now is the time to work on it, on your own, so you don't repeat the same issues again in the future.
Oh, and its not easy. I had to do something similar, but with a guy I had only 3 dates with. I felt terrible telling him I didn't think it would work; I wasn't feeling a romantic connection and realized that I wasn't emotionally available. Unfortunately, it had little to anything to do with him, and I told him that. I imagine it will take more courage after having a R that lead to an engagement. But, you AREN'T married. (Think, Big Girls Don't Cry by Pink).
