Dear Junior's owners,
After looking at Junior's blood test results I would choose Derma-IonX because it contains some of the more commonly used homeopathic remedies that support the kidneys. Other things that I have used with cats that are having high BUN levels are fluids, the addition of digestive enzymes to the food (which should contain easily digestible protein,) and probiotics. It is important to help the body to break down the food completely so that it doesn't put more stress on the liver and kidneys. Your veterinarian may suggest a special kidney diet. I would use canned food if Junior likes it. Then you can add a little purified water to it if you need to increase his water consumption. Also be sure to offer purified water for drinking that is free of chlorine and fluoride.
I hope these suggestions give you some hope. Please let me know how you progress because I would be happy to answer more questions for you and offer more suggestions. I have known quite a few cats that have gone on to live good lives despite a grim initial prognosis.