It isn't your "fat a**" or whatever he said that is his problem. I am seeing him as still EXTREMELY obsessed with her. I don't know why. He may be talking himself into hating her, or whatever - but there is really a very thin line between love and hate. His emotional involvement still runs deep - whatever his feelings. And he's bringing that home to you.
IMHO, he shouldn't be discussing most of this stuff with you (unless you ask). He really, really should see a therapist or at least a trusted friend (not who is friend to OW) to work his feelings out. I remembered you both having sex before - but that is probably because he was happy and had both of you. Now he's likely going through some sort of withdrawal and obsessing about her. I think its probably because it didn't burn out naturally - it was forced to end (and hopefully it has).
Maybe you should go to a counselor by yourself? And good for you on spending some money - he's been spending your money on her all along. (just don't go overboard). You should definitely work out and get healthy - but for yourself first, and it will be a boost for your other relationships in your life too.
