Well, I'm not sure what I did, but my battery is behaving like its old good self again.
I did a third reset and this time I did not restore my previous apps and settings. In fact, I installed nothing at all. I just picked a built-in watch face (dual time) and kept using it, observing the faster-than-usual battery drain for 2 days straight.
Then one day I took it off the charger at 7 am (as usual) and the next time I looked at it around noon, it was at 58%. When it accelerated down to 47%, I put it back on the charger for 15 minutes until it got to 55% and I had to be on the move again.
As I watched the drain in real time continue, I turned off the AOD, which slowed the rot, but it kept going regardless. When it finally hit 18% and I realized I needed a time piece for 8-10 hours still, I turned on Power Saving mode.
I put it back on the charger at 3% and when my phone asked me if I wanted to turn off Power Saving mode (when it hit 100%) I said yes. When I took it off the charger, I turned AOD back on and noticed that the battery wasn't draining anymore and behaved normally thereafter.
I have since installed Facer (and a custom watch face) and set up Samsung Pay. So far so good.
I'm not sure which of these details was the key, but I provided all these details so that someone else may find a solution to their own problem.
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