If you were wondering whether I was able to fix the faucet until today, oh my faithful readers, then rest assured, no progress was made.
Despite the quite encouraging diagram find a couple of days ago, when I disassembled the faucet again last night, no set screw was to be found and the cartridge would not come out. I decided not to put it all back together again, but rather to take the parts to Ferguson and see what they would come up with.
And so this morning before work off to Ferguson's I went to ask for help and to surrender the borrowed tools if no useful ideas were provided.
Today there were a few people there, all quite knowledgeable about this sort of stuff, and upon some deliberation they all agreed that I just did not yank the cartridge hard enough. The theory went, after what could be easily more than twenty years spent in the pipe, the cartridge was set in there with sediment and I could try and break it loose by trying to wiggle it side to side gently.
What do you know, after a fair amount of prying with a screwdriver to scrape and break off the sediment, and some determined wiggling and yanking, the cartridge finally gave and came out!
It was the exact part that I hoped it would be, and so less than 15 minutes later the new part was installed and the whole shebang happily assembled. Tomorrow I will drop off the tools and hope this cartridge holds for another 20 years.