I'm very sorry to hear Tubby hasn't been feeling well. He's such a big beautiful black boy, I will say some prayers for him that he has more time with you. It doesn't really sound all that bleak though and I was wondering the same thing as Slick, has Tubby had a dental done anytime recently? Could it be his teeth?? I know it's also very common for cats with kidney disease to not have an appetite alot. The sub-q fluids should help him also.

I'm glad to hear he's more alert and seems interested in things again, that sounds very good! Wishing Tubby and you all the best!