OK, I may have solved this problem. Days ago I found that thread that said to reset all the battery optimization settings. That seemed to work for a few hours, but then the phone started getting warm and burning through the battery again. Fail.
I kept reading through that thread and some owners said they also reset all app permissions, which worked for them. I've since done that and it's now been two days since I've had the battery problem. I've never gone that long since this started without the phone heating up and sucking down the battery. The phone stays nice and cool (other than when I wirelessly charge, which was normal before Android 7 for it to get warm), and battery life is better than it's ever been. The only app permission I've reauthorized since the reset are those requested for AccuWeather.