Wow, this is hard but you have come so far. Keep focusing on the positive. He is at least considering breaking up with the OW, if not planning out loud how to do it. He acknowledged your changes. He thanked you. He felt heard.
I hear the EXACT SAME THING from my H - that I've hurt him through blame and I want to say well he's hurt me through blame too but I don't. If we want them to continue to take baby steps, they need to feel safe. That means feeling heard and validated. That means no pressure, letting them make their decisions on their own. They have to know inside themselves they want to be with us, not that they are coming back out of any pressure or input from us. You handled this beautifully. Yes, it feels like a post-car-crash trauma afterward. You took care of yourself and did everything you could do. He's moving toward you and you are letting him do it on his own time frame.
I think the pullback he's exhibiting is natural. He is pulling back to process his own feelings. You need him to do this so he is sure he wants the R with you. You need him to come to you. Great job!
these are all positives. You are farther down the road than a lot of us, and than you ever were before. Keep that in mind!
