It now appears the source of drainage is the area between a wisdom tooth that grew large in the past year and the tooth next to it.
There is some purulence, for which I'm using amoxicillin, waiting for Augmentin.

tt began so soon after the extractions and the slowly-resolving fistula that it has taken me from October 6 (the double-extraction date) to now to realize what is actually going on,. even though my previously straight bottom dentition has gone crooked over the years - because the drainage is in the same area but right below it and there are no other symptoms.

All the teeth on the bottom are still in and my own, except for a 1-tooth bridge put in about 3 - 4 years ago.