My thoughts and prayers are with you and Ripley...We lost our beloved Billy (who was also 17) last June to CRF (chronic renal failure), so I know exactly what you are going through.
It does sound as though he is/was quite dehydrated. How long have you been giving him sub-q fluids?

I'm very glad to hear that you were able to get Ripley to eat something... Often when they don't feel well, they just won't eat, so if he's eating something, hopefully that means he's feeling a little better.

The fact that he is in his hiding place is a bit concerning...Cats tend to hide when they are sick, so, and I'm sure you already know this, keep a close watch on him. They can go south quickly with kidney failure, so it's very important to really keep an eye on him. During the night, if he seems to worsen, I wouldn't hesitate to call your vet, though. In the meantime, hang in there, and know that we are all praying for you and for your Ripley.

Judy

P.S. If anyone is interested, there is a candle group at Light a Candle called "PURR" for cats...I just lit one for Ripley...Every little bit helps...