Ok, was not thinking I would mention this because in the moment I wasn't 100% sure of the vibe. But, he was definitely looking at me with intensity. Not sweet and loving, but there was some kind of electricity coming from him. At one point, he came very near to me as we were leaving (I seriously don't think I have been that close to him in years), our faces were very close together and he was looking very deeply into my eyes. In the past he would never have gotten this close to me and, having done so, he certainly wouldn't look me in the eye. I wasn't sure whether it felt menacing or what (was he trying to stare me down?), but it was very different than the cold fish thing he normally does.
My top contenders for not letting go: 1. Fear--I believe he is borderline and he is terrified to let go. I think it is mostly about him; 2. Control--he really likes to know what I am up to and make me have to come to him at times--yank me around with money, insurance, etc.; 3. Possession--I think he thinks he owns me and yes, that I am sitting nicely on the shelf for him; 4. Triangulation--I do think he uses me to triangulate the OW, make her work really hard with the threat that he can always come back (or so he thinks); and 5. Marriage-proof--since he is messing around on OW2, no doubt he realizes she isn't "the one" and he doesn't want to get stuck as you say Job.
Son is struggling, but a lot of it is his own making. He has a tough few days ahead because it is finals and then can take a mini break and pull himself together. Hopefully OD will show up as he said for him next week. I have also made an appointment to consider medication for him. Not something I want to do, but may be necessary.