My cat came home for Christmas Eve. He's on the mend and at home now. He wasn't eating much at the vet, so I brought in some of the cat food I've always fed him and left with them one more day. I decided that if he didn't recover by the New Year that I was just going to have to put him down rather than have him suffer.
So on the morning of Christmas Eve, I went in to check on him and found that bringing him his usual food was what did it. He'd started eating and his body temperature was back to normal. So the vet let me bring him home. He's still skinny and weak, but he's not wobbly on his feet anymore and getting better.