Just checked on Taco. He was lying on his side at the bottom of the tank and floated up slowly for air. I lowered the water level to just a few inches and took the heater out (I'd cook him if I left it in).
At the rate he's going, I wouldn't be surprised if he passed in the night. If he recovers, it'll be a God-given miracle.
I'm out for the night, folks. Updates in the morning. Thanks for all of your well-wishes, support and prayers, y'all. I really appreciate it a lot (and so does Taco, I'm sure).