Thanks guys for the observations. It was surprising, but only time will tell if he keeps it up, builds on it, or falls off again. Son did have a good time and I think felt much closer to his dad. Because he really doesn't understand this stuff, he said "I think he likes me better now that I am older." I don't think he gets that dad is coming around now because he's been in la la land for years and it had nothing to do with son or his age.
As to the OW, hard to say if it is just the dying limerence and he's shopping for a new one, and killing time in between or whether he is legitimately waking up a bit (I think he's off the dating site that used to send me his profile). I went to breakfast with my mom and S. S repeated over and over how his father seemed so normal and relaxed. He talked about some of the things they talked about. He observed that his father is a peace-loving man who is very opposed to war. This is how I knew my H, and then he went into MLC and at some point bought the guns. I rather wonder what is up with those these days. Son also said that the coat I told him did not look good on him was nowhere in sight, replaced with a fleece that bears the name of D's college.
I got what I guess is a temperature check from him today. A business email on a matter with no urgency, but not nasty or cold like in the past. If anything I'd say a little tentative. Coming on the heels of the visit yesterday and that we have not spoken in two weeks, I think he just wanted to see where I was, keep dialog going, etc. I thanked him for reaching out and responded in a neutral fashion to the matter and told him I would follow up later when it was concluded. And, as is now his habit, a quick response thanking me. Big change there.
Son has a big tryout this weekend for the national team he was recruited to last year. OD actually wished him luck. Son said he was nervous and OD said of course they are going to want you. More signs that the man I knew is in there somewhere. Last year he didn't care when S was selected.