He even said that he checked with his friends, and the pub I am going to tends to get a line outside by 9, so he'll take care of the kids so I can leave earlier and not be stuck in line...!!!???? whaaaa?
Allowing myself to go into sherlock mode.
He checked about the pub you were going to with friends? Like in asking his stag friends if that is the kind of place singles go to hook up? That kind of checking?
I'm a teacher. I live surrounded by late teens all day long. I know who they are and their physical side. Young and fit.
But their appeal stops right there. There isn't enough of them in terms of personality to please a grown men. Maybe your STBXH is beginning to realize this just now.
Or it can be that he still wants to part in good terms somehow and feels guilty about all that went down. You're his kids mother. I guess you're going to have to keep waiting for developments.