I would go by your veterinarian’s recommendation. Your dog is a senior and has a medical condition that will not go away.
Outrageous ($$) is when the dog becomes very sick and you have to go to the emergency vet on a Sunday evening.
Some science based veterinary medicine here
More Nonsense from Holistic Vets about Commercial Therapeutic Diets
Homemade Diets for Cats and Dogs with Kidney Disease–Most Recipes are Wrong
Check the comments too. You can post a question if you wish, but the veterinarian cannot give you specific advice as he has not examined your dog.
Good luck
PS: There are no veterinarians here at DFA.
