I'm so sorry your bully is having those issues and you haven't found a solution.

Since you've ruled out genetics, it could certainly be something he ingested or at least came into contact with somewhere at some point.
I know dogs like eating grass from time to time and with it being spring time and all, people are putting down fertilizers, herbicides and all sorts of chemicals for their grass and soil. Any one of those things could potentially effect dogs negatively just from walking on it. Just a thought.

I prefer a raw meat diet for my boys, but that got pricey recently, so I mix raw & kibble. I used blue buffalo for a while in a 50/50 ratio with Victor hi-pro plus, but I moved on to a 50/50 mix of ACANA red meat recipe and TRUE MEALS multi protein (they just lost interest). I still feed them raw meat, but I'll adjust the ratio depending on time of year. More meat and less kibble in summer and the opposite in winter.

I would personally stop all kibble unless the vet prescribed some. I'd just make plain white rice (clean the hell out of it before cooking it!) and boil some chicken. Melt a few tea spoons of coconut oil (raw & unrefined stuff) and pour it over the rice and chicken and let him go to town on it.
I would do this at least until you figure out what the problem is and what's causing it.

As far as the kidney issues go, that's more complicated, but again it could be caused by something that he ate or came in contact with. That's why I mentioned the grass; he could simply be stepping on lawn with chemicals and absorb it through his paws. One of my boys had renal issues when he was tiny and I gave him these drops that I bought from Amazon and while I'm not saying that this WILL cure your dog, I believe that it saved mine or at least bought me more time with him. They turn two this summer, so we have a while to go still.

https://www.amazon.com/dp/B01N7VZQZW/ref=cm_sw_r_apan_i_9M3MH8F12E7ZZ2HYNAM2?_encoding=UTF8&psc=1

I hope some of this helps.