It may help you to look at this website which explains how kidney failure is staged in cats and dogs. The higher the stage the more severe failure is present and the more guarded his prognosis is: http://www.iris-kidney.com/pdf/IRIS2009_Staging_CKD.pdf
This may help you ask your veterinarian the right questions that will allow you a reasonable estimate of his prognosis.
Ideally he would eat a diet balanced for kidney failure such as Hills k/d, Hills g/d or Purina Veterinary Diets n/f. I understand that he wasn't eating well for you thus you are feeding a homemade alternative diet.
Animals with kidney failure need high quality but limited levels of protein. The kidney is responsible for filtering and keeping proteins in the bloodstream. If we overload them on lots of low quality proteins then we over-work already damaged kidneys. We also need to stay away from foods high in phosphorus as the kidneys are responsible for getting rid of excess phosphorus.
I understand he may not be eating well at this point. Things you can feed to perk his appetite are green beans, peas, squash, mashed potatoes, sweet potatoes, rice, noodles, and carrots. Small amounts of cantaloupe or watermelon are fine too. If he won't eat his dog food small amounts of white chicken, cottage cheese and boiled or scrambled eggs can be added to boiled rice, noodles or mashed white or sweet potatoes. It is very important that he eat but we do want to move him towards eating dog food balanced for his condition if we can. So mixing some things in with his dog food initially if he won't eat it is fine. Just try and limit the amount of protein and make it very high quality.
Stay away from fatty meats, lunchmeats, organ meats and salted meats. Organ meats in general are high in phosphorus. Phosphorus is an electrolyte that failing kidneys have difficulty removing. If the blood levels of phosphorus are too high calcium is leached from the bones leading to weak bones and calcification of the kidneys.
As far as beneficial treatments fluid therapy to keep kidney waste products at a low level by flushing them out is often beneficial. Usually we start with intravenous therapy at the veterinary clinic then use subcutaneous fluids long term to manage the levels. You can learn to do this at home.
Supplements such as Azodyl to change gut bacteria to help decrease urea in the gut which would be absorbed into the blood, and epakitin to decrease phosphorus levels can be very helpful.
Medication (such as enalapril) to control secondary hypertension and protein loss into his urine via leaky kidneys may help.
If he isn't eating well and ulcers are a concern then sucralfate, a coating medication, can help heal gastrointestinal ulcers which will improve his appetite.
Acid reducers to try and settle his stomach and improve his appetite are also useful. Either:
1) Pepcid-ac (famotidine) at a dose of one half of a 10mg tablet per 10 to 20 pounds of body weight every 12 hours.
2) Prilosec (omeprazole) at a dose of one quarter of a 20mg tablet per 10 to 20 pounds of body weight every 24 hours.
These medications are quite safe and can be used for several days if necessary or for as long as necessary.
I also recommend an omega 3 fatty acid. These are natural anti-inflammatories and have been proven helpful in dogs with kidney disease. Reputable brands are 3V Caps and Derm Caps.
Finally if bringing down his waste product levels and controlling stomach upset and hypertension isn't enough to keep his appetite up we can use appetite stimulants. Dogs that eat and maintain body weight are proven to do better in the long run. Mirtazapine or cyproheptadine are both worth trying. They have different mechanisms of action so if one doesn't work try the other.
If you find that he will not eat the kidney diets and you need to feed a homemade diet all of the time I recommend consulting with a veterinary nutritionist to design a diet for him. There are recipes available but a recent study found that none were balanced appropriately.
Here is a link to help you find one in your area:
Another option is a company called BalanceIt. They sell trace mineral and vitamin supplements to add to homemade diets to make them balanced and will help you formulate a diet for her. Here's a link to their website:
Best of luck with your boy, please let me know if you have any further questions.