I sometimes think your T (and other "boundary ninjas" too) might be terrified of what might happen if he were not super rigid about every boundary ever. Maybe he had a transgression in the past or maybe he saw it happen to a colleague, who knows. But it does lead him to be harsh I think. Many T's will cross boundaries -- I don't mean the big ones, but some of their general everyday boundaries -- where it is of clear benefit to the client, which in your case right now, it seems like it would be, to help repair things. I know it might feel foreign to meet with a T who is not a boundary ninja, but it might be worth giving it a few sessions. Can you manage two T's for just a few weeks?

I think T's should try to be consistent over time, and certainly shouldn't go in the direction of becoming colder. And -- maybe I shouldn't say this, but -- he made that absurd statement about therapy being a medical procedure on the same day that he -- "apropos of nothing" you had said, brought up affairs. My T says that seemingly random changes of topic can be illuminating and that's why he doesn't direct the conversation in session. Your T made a really cold (and incredibly patronizing) statement about the therapy relationship and then mentioned affairs shortly after that -- I feel like he could be afraid of closeness with clients and if so, I imagine you're being hurt by that. (I know I'm speculating, just sharing my spidey sense on this one? Which is worth what you paid for it!)

If your attempts to explain your feelings just feel like a bid for closeness from him, and he just keeps getting icier and more boundaried because that bid for closeness makes him uncomfortable or afraid -- I'm not sure how to remedy that dynamic. If it were me I would ghost, but then if it were me, I'd have ghosted at the "medical procedure" comment.