I think he's got his cake and is eating it too. Cavorting around with OW, sees his kids whenever it's convenient, has a nice dinner waiting for him, stays 90 minutes, then hugs you good bye and is off. Sounds exactly like my H. Except I don't get any hugs. I think your H is trying to convince himself he's such a nice guy, he still hugs you, still cares about your feelings--but then he goes back to OW anyway. But he's a really good guy (in his mind) because he hugged you and saw his kids.
Believe me, I did this too. There were a couple of weeks back during the summer when H missed D so much, and he came over to visit every evening, I had a nice dinner (which he never acknowledged, just ate) and stayed out of their way. I saw it as wow--something's changed. It lasted 2 weeks, he rarely acknowledged my presence, if I tried to leave to run errands he'd need me to be back so he could leave. I felt like such a doormat, and so stupid.
M60 H52 D20 M14 yrs OW-old gf from 1986 bomb-5/18/08 H filed for D-9/10/08 D final 4/24/09 xH remarried (not OW) 2012