After a little soul-searching, and deciding I didn't want to harbor anger, I helped him with the ones I remembered each time.
Had I actually been hit by a bus, that wouldn't have been possible at all.
I'm sure that if I'd hit the lottery and gone to Fiji, I'd have been even more likely to help him with those passwords.
In the end, not-burning-that-bridge did help me earn more money as he hired me back several times, and I demanded more money each time until I was asking almost as much per hour as he was getting from his customers and he simply couldn't afford me.