The perhaps inevitable conclusion of my faucet drip fixing attempt is that now the hot water cannot be shut off. (Unless you shut off the source valve, which I did.)
I do think the actual fix was going to be to have to get a new faucet anyway, so we’ll end up at the same spot anyway, which will hopefully be that a new faucet is installed with some struggle tomorrow, rather than we have to call a plumber so don’t use the upstairs sink for a week.