I peeked in on him when I woke up this morning, and his face was swollen on the left side to about 3 times it's normal size. It literally looked like he had shoved a marble into his mouth. I was really freaked out, so one of my friends agreed to take him to the animal hospital. We discovered a couple interesting things:
1) Spencer is A LOT older than I originally was told. I thought he was 15, which is pretty old by our standards, but he's probably at least 20, because...
2) Spencer has snakey osteoporosis. Yup, he's losing bone density. And that caused...
3) Him to break his jaw. We're all just guessing here, but he may have been randomly striking at something (even his last meal - he still has a good feeding response with f/t), and it broke due to the low bone density. The doctor had to reset his jaw, then do more x-rays to check. Total time at the vet was almost 3 hours.
So Spencer doesn't get any meals for 6 weeks MINIMUM (poor baby), and needs regular calcium supplements. Because I obviously can't pill him while he's recovering, he's going to get a calcium-powder paste injected in the side of his mouth with a plastic syringe. After that, I'm going to start pumping his mice with extra calcium.
The swelling is almost entirely down now. I bumped up his hotspot a couple degrees too. I figured he might enjoy a little extra warmth, and he has his head directly on the heater. He doesn't seem to have problems drinking, so that's huge relief. Problems swallowing would've led to a whole new set of problems.