I have to say, I've been in some turmoil ever since B.'s BF called me Sunday before last, saying B. was now "homeless." But that's all starting to sink in now, and I'm OK with everything (and B.'s not homeless). As I'd said, my offer to rescue B. from his situation was not accepted (just as well, but I'd felt compelled to do it since I'd made a commitment to him and hope someday -- maybe after I'm dead -- he remembers that). (He'd also made a commitment to me, which apparently he forgot or was not in a capacity to make in the first place.) I also gave him the number of a gay men's domestic abuse hotline and recommended he talk to his doctor.
I would not have accepted B. back here unconditionally. The proviso was that I would have to be able to trust him. Under the present circumstances, I really can't, especially not with the BF in the picture. Which is fine since he's not considering coming back here anyway. (Before B. left, he was letting the BF into the apartment behind my back, and an Amazon credit card, which I only use at home, went missing, and there was a charge made on it I didn't make, etc.)
So everything's back in a steady state right now, and the air has been cleared somewhat. I know where I stand. It's a relief.