You are still sounding good. Sorry about the last bit.
Two words of advice -- TELL HIM why you are pissy "I am very hurt and confused, which I'm expressing through anger, because I was feeling closer to you this weekend. But when we got back friend let slip that you had pretty much been living with OW and I noticed that you emailed her from my house. I feel pretty deceived and betrayed by these things."
Second, slap slap, YOU KNOW NOTHING. Re his email...
He could have meant:
He wish things hadn't ended.
But, I expect he meant something like...
Things have ended, but he wishes she wouldn't have been so hurt.
Things have ended, but he wishes she wouldn't be threatinging to tell you everything.
Things have ended, but he wishes she wouldn't have turned into a psycho b*tch.
Things have ended and he really wishes she wasn't going to sue him for sexual harrassment.
Things have ended, but he wishes they could be friends.
(This last is pretty standard for all As. People want to feel like it really meant something, that they really cared for the person, etc... It makes them feel better for awhile because they can't really face the ultimate pointlessness of the A.)
So, anyway, I expect he was much closer with you this weekend because he has ENDED it. But, you are right that you don't want to act like everything is hunky dory too quickly. He is obviously still working through the break up.
Remember, you only want a new R with SO that works for you. You are acting like you are starting a new R with him, so do not allow it to include things that don't work for you.
