I hear your frustration - and anger. I say that with total empathy for what you are dealing with because of my troubles with Jeddie the first year or so that I had him.
You would not see yellowing of the eyes with kidney issues - it is jaundice that causes that, liver failure/disease. Renal failure/insufficiency is usually a very gradual process with aging. Sometimes a toxin can cause acute kidney failure, but it is so sudden that the cat is obviously very ill. The usual signs are excessive thirst and peeing (PD/PU). Other diseases that cause PU/PD are diabetes, hyperthyroid, hypercalcemia (high blood calcium levels), diabetes insipidis, Cushings, Addisons, Acromegaly, medicine induced and behavioral. That's not a complete list, but covers the basics.
You are dealing with inappropriate peeing, which
can be caused by physical disease, like a UTI, but I think is more likely a behavioral issue. If you found that Prozac (flouxetine) doesn't work for him, maybe you could ask the vet for an alternative medication.
When I got Jeddie he was exhibiting OCD symptoms like over grooming, but he was also peeing on my carpets and on the front door. He did confine himself to the carpet and some boxes in my second bedroom, so at least I didn't have to sleep or sit on it. I did end up having to rip out the carpet though. I tried everything: more litter boxes, Feliway, begging, yelling, Simple Solution. He started peeing in the bathtub (at least its an easy clean up) and in a tray I had under a litter box. Nothing deterred him. I got to the point where I told him he was signing his death-warrant. I finally tried Prozac and it was like flipping a switch. He has been on it a year now. I did try to ween him off it at 6 months, but he peed on the front door after about 3 weeks, so that was that.
You might find some useful info on this site:
http://www.marvistavet.com/html/body_feline_house_soiling.html
Maybe a Feliway diffuser would work for him?