Bluesea, this happens sometimes. Especially when you get really good at detachment. Where the spouse is expecting certain reactions and behaviors, and you don't react. Then they start to rethink things.
Also, I think his kids reaction to him are having an effect on him. He thought, like most lying cheaters do, that he could do whatever he wanted and everyone would just go "oh well" and he'd have no repercussions. Some of them don't care at the time and regret it later. Others realize what they are set to lose, and want to try to correct it immediately.
So I think the exchange last night has him questioning himself. So I think he may really be considering ending the affair, recommitting back to the marriage because of what he stands to lose. Lots of WAS threaten to leave, and when you call their bluff, they really have no where to go! One of the things my W said was that when she said she wanted a D, wanted to get a job, and wanted to get her own place, that if I had thrown her out right then she would have been screwed. So you do have to be careful here.
He might be buying time. Or he might be sincere. The problem is that As are addictions. And most people do not just quit addictions cold turkey and move on. That is difficult for the addicted person to do without help.
The good news is that this changes NOTHING that you should be doing. GAL, 180s and continue to work on detachment. Do not overreact to this. Do not celebrate. Do not count your chickens. Give it time. Give him space. Give yourself time and space! Que Sera Sera. What will be, will be.
M(53), W(54),D(19) M-23, T-25 Bomb Drop - Dec.23, 2017 Ring and Piecing since March 2018