Karen, He bought a celebration cake to celebrate his moving out? How ignorant! Did he tell the kids that's what it was for???? Actually, him doing stuff like this to hurt you is emotional abuse. Document all of it!
I'm so sorry he has to hurt you like that. It's so childish. And he certainly isn't the tormented victim here. GoingForward has a good point -- he could have been trying to get a rise out of you. He'd probably like to see you explode so he can stand back and say, see why I want out of this M?
I'm glad you told your friends what was going on. You need their support.
As far as OW and her family... boy oh boy is H getting into a bad sitch! His little fantasy world is going to crumble fast. If a had a million dollars I would be betting that this R is not going to last! A new R or M does not make your problems go away - they are just carried into the next R.
Get out with the kids this weekend. Leave him out of any activities. He isn't good for your PMA. (And throw that cake away.)