Hi Sliver! Just dropping by and I saw your post. I've been in the same sitch too, with lots of anger after 2 years of separation and one year after the D. In fact, he's actually gotten angrier and less cooperative since the D. My theory, and I could be totally wrong, is that your x and mine are probably really angry at themselves for mistakes they've made, but they put the anger off on you instead. Easier to blame someone else, than to look at their own mistakes.
I also think from what I've seen that our x's have a fairy-tale ending in mind for themselves after the D, and I don't think that usually happens. I bet your X is having a hard time dealing with your gf being in your d's life.