I lost a dog to kidney disease many years ago. This is a very serious condition. You should be working closely with a veterinarian.
My dog needed sub-q fluids almost every day the last 2 years, prescription dog food (canned) and plenty of water, nothing else. No supplements! Just prescription meds. Discuss with your vet.
He doesn’t want to eat because he is probably nauseous, in pain, hence the vomiting. I would not try to force him to eat.
The next thing that will occur after kidney failure, if it hasn’t already, is uremia. The dog smells like urine 24/7. It emanates from his pores.
Difficult decisions ahead
Your dog needs the expertise of a veterinarian, not the internet.
Good luck
