For what it's worth and I know it doesn't help much -- he's feeling very crappy about himself right now; he KNOWS he's being a butt both to you and to your girl.
I LOVED Lissie's advice/quote and you know what? You have a lot of strength and a lot of class. I think he's partly pushing you to see if you'll act like his ex so he can say, "See? She's a b**ch too" Don't do it -- respond with class and let him be the bitter hag. Right now, keep it about your girl, follow Lissie's lead and hang in there.
I know that comes off sounding SO much easier than it really is -- you are deeply wounded. But one thing I do know to be true for me, anyway; when I am struggling it very often helps ME to have someone else to "take care of" or help out. Right now that someone is that little mini-you with the greatest smile
