Hello and thank you for asking your question on just answer. My name isXXXXX will try to help.
You could use one of the oral heartworm preventative such as "heartgard" (ivermectin and pyrantel) or "interceptor" (milbemycin). Both are very safe and should not affect the kidneys.
The company that makes revolution says that it is quickly absorbed through the skin into the bloodstream then redistributes to oil glands where it can stay for a month or more to kill fleas. Revolution passes through the kidneys unchanged and 5% is excreted in the urine. It is probably not the best choice for him.
If he has a problem with fleas, other options that are probably safe for renal failure cats are fipronil (Frontline Top Spot or spray, which is topical and doesn't get absorbed) or a combo of monthly Program (oral flea prevantative) and weekly Capstar (oral tablet that kills fleas). You can buy all of these online. Spraying the environment with an IGR (insect growth regulator) helps a lot also.
If he is not having a flea issue, and you do not have a lot of fleas in your area, then I would not treat him for fleas unless you see fleas on him. You could get a flea comb and comb him periodically to check for flea dirt and fleas.
The same goes for heartworm prevention. Ask your vet how many cats they see each year with heartworm disease. If it is not a big issue in your area, then maybe he could skip that medicaiton as well.
I agree with you that the less his kidneys have to filter the better.
To be honest, I only treat my own pets for fleas when I see a flea. I do not want to put extra chemicals on them if they do not need it.
Do not click accept again. I was just typing more and I did not know you were going to accept the answer right away. But thank you for doing so.