I've been through this several times also, and it's such a roller-coaster ride of highs when they eat well and look totally relaxed when they sleep, and lows when all their body functions seem to go into disorder and they look miserable. I guess Max threw up because he had difficulty pooping, the straining would have pushed up into his stomach, at least that's what I've always thought with mine. I just lost foster Alexander to renal failure and he had a really difficulty time in the litter box, leaving part behind and dropping pieces on the floor as he walked, and towards the end simply walking away from his dish and pooping on the kitchen floor. As I said before, it seems to disorder all their body systems.

With all of mine I used to give fluids every other day, then every day, then twice a day as the renal failure progressed. However, they do reach a point where no amount of fluids given in any way will take away the dehydration.

I'm really sorry that you and Max are going through this very difficult time. Is he still enjoying attention? (I didn't read through the whole thread since, like you, I post at work and have a tough boss.)