OK, I looked at my receipts, and it's not quite as bad as I said. The most recent BB was installed 3 years ago, and is this one:

https://www.amazon.com/dp/B018HHRC6W made by Wheels Mfg.

I installed it, as well as the earlier BBs, including the original, which lasted a good number of years. (to one of the Qs--I'm positive the problem is the BB, since I took the cranks off, and found the difference in bearing feel, as I described).

The one thing that is different from the original install is that I switched cranks from a SRAM crank to one compatible with Shimano, and needed the following adapter:
https://wheelsmfg.com/bottom-bracket...o-fsa-etc.html