These two situations where you are beating yourself up for bad judgment are indeed very parallel to each other. Both what happened and how you feel about it:
And like a total moron I walked right into it. Texted him back, told him I could talk that evening. He called me a little later and what transpired was 2 hours of him punishing me.
We got home, I said goodnight to Kiddo, went over to give pwBPD a goodbye hug and he suddenly was very sad. "Come with with me on the couch... ."
And NO. I am not a dumb person. This is why I don't recognize myself anymore. Can any good come from sitting with him on the couch? HELL NO. Did I do it anyways? Ugh. You bet. And an hour of circular conversation later all we have established is that he has been trying to be happy and positive all night but I haven't opened myself to it and that I'm socially retarded like his ex wife.
In both cases, the first thing you did was not stupid, it was a kind and generous thing. You gave him a chance. Accepted the offer to sit with him on the couch. Invited him to call you later.
Yeah, he's used up a lot of second chances, but offering him another one is still a good thing.
The place you went wrong was staying through the circular argument, punishment, etc. for hours.
Next time, do invite him to talk on the phone (as fits your schedule). But when it turns ugly, "Goodbye, I gotta go" or "I won't/can't listen to this anymore. Bye." (Note: You do NOT need to identify WHAT you won't listen to, he might well be smart enough to figure it out... .and if you try to tell him what it is, you end up in a circular argument JADEing all over the place. Hang up instead!)
Or next time, when the conversation on the couch turns to what you are doing wrong and that you don't understand/appreciate all he is doing right, just GO. Not after an hour. In less than a minute.
And most important, be gentle with yourself. Yes, you wish you hadn't done a bunch of things like this, but learning this is HARD, and learning to actually do it when you are in the middle of it is harder. If you are like most members, you probably learned you were supposed to do this as a child. You will figure it out, you will do better next time, and beating yourself up isn't going to get you there any faster.