I cannot be of much help. End of last year Filou had an infection on top of his renal failure and I was afraid his time would have come.
He refused to eat, hid quietly in places and I could see he had problems walking and jumping (jumping is an important thing for Abys).
We went into handfeeding whatever he liked and making sure he got at least 100 calories per day (egg yolk, ground beef, cream, goose fat...).
Then on top he got diarrhea (maybe too much fat) so the vet said not to feed him 12 hrs, then after it came back, a full day. He was down to 2600 g and I remember I wrote all my Christmas cards saying that that may be his last X-mas.
After the diarrhea stopped and the infection was treated he came back into the world. He is eating now and we have him at 2900 g. He walks much better and jumps again (although not so high than when he was young- but so do I ). He is definitely feeling well.
The vet has stopped to check his levels- we all know they will be over the top and she says she never saw a kitty survive that long on such high levels. But as she is a friend she sees him also privately in our house and she agrees: he is ok.
So I cannot say whether Taz' time has come- he may get over it and that's what I wish for you.