I guess I owe the world and my future self an update about Windy.
He has not been eating much of anything all week, despite the fact that I've been trying to tempt him with various things. Wednesday and Thursday I had to force feed him his thyroid pill. But aside from not eating, he seems to be more energetic than he was a few days ago. Despite the fact that it's 20°F outside, he made two loops all the way around the yard before he would come in after I let him out to pee, and after a few minutes he wanted to go out again. Because of the weather I left him in the house for the day, and I think he was actually feeling well enough to be bored. This evening he was actually interested in the spoonful of food his thyroid pill was in, and he ate several biscuits and even a little of his regular dry kibble that I left out for him. Obviously he can't go too long not eating, but I'm really reluctant to treat just his refusal to eat, without other signs I can see to back it up, as the sign that it's time for the final trip to the vet -- especially since it is torture for him to travel by car, and I really hate the idea of forcing him to take a car ride to the vet so I can kill him. If we're lucky, tonight is the sign that he's actually coming around.
I have stopped giving him the melatonin pills. It seems like a real long shot, but he first started to be real sick not too long after I started giving him the melatonin, he was off it when he spent the night at the vet and he seemed a little better when he came back, and now he's showing some signs of improvement after being off the melatonin for a couple of days. Maybe, just maybe, his current acute problems are some kind of a reaction to the melatonin and if I'd just stop poisoning him with the stuff he can be OK again.
Good thoughts are certainly appreciated. I know that the best I can hope for is that he'll be with me a few more months. I'm a little depressed about it, but either I'm going to be able to handle it better this time or else it's just not really going to hit me until he actually dies.