I think "being himself" includes being free to chat up all the available young women and develop inappropriate relationships with them, whether it descends into a physical relationship or not. It’s back to “being married but acting single.” I suspect you’re finding out things about his recent conduct (that you don’t want to discuss here at MB) that tend to confirm that analysis and that’s why you’re in such a gloomy state of mind.

He can go from affectionate to hateful in a single afternoon because he’s been in contact with another of those young women, whether it's a new OW or any of the others he’s been in contact with in the past. It’s fairly typical to see a radical change of mood like that when they get a “fix” of contact with an OW. His mood may change again this evening. You seem to have stood up for yourself and he seems to react to that by becoming conciliatory.

I’m becoming more and more convinced he’s never been out of contact with some OW, TFC, and I think MC is the only hope to fix this thing. Hang in there, if you possibly can until your MC returns.

If you can’t, your Plan A was better than most and I believe a good, dark Plan B will be that much more effective because of the work you did in Plan A.

Stay strong, TFC.