Sounds like you've been doing your fair share of doctoring lately... I'm surprised your urologist hasn't done a C/T contrast scan. I would avoid a biopsy unless they're certain it is necessary. (Just my opinion)
I had gross hematuria (visible blood) in my urine, and large clots that were difficult to pass. I never did have any pain (urinating or in my lower back) until the blood became a constant. They suspected kidney stones... a C/T scan showed a 'blur/shadow' in my left kidney and I was rushed to a urologist.
He did a contrast C/T (you 'get' to drink this nasty-tasting stuff) before the scan and it shows all kinds of things. In my case, that 'blur'... Since I was running a fever, they did all kinds of blood work, and suspected the blur was a mass of coagulated blood caused by a kidney stone. They placed a stint between my kidney and bladder to keep it open so I could pass the blood/clots. Three weeks later, it was still there, and due to the location of the 'blur' (in the renal pelvis) decided the kidney had to be removed. I did not have a biopsy.
After surgery (which left a 10" scar under my left bottom rib) my doctor told me it was cancer... he didn't know what type, it was something 'uncommon' so they sent it to Mayo. The type of cancer I had was Urothelial Cell Carcenoma (which is a transitional cell cancer usually behind bladder cancer) and was graded a Stage III tumor. Even though it was contained in the kidney, it had gotten into the main artery that blood leaves the kidney in. The associated lymph nodes were okay.
As you've no doubt learned, Renal Cell Carcenoma is the most common type of kidney cancer. After my surgery, I went to Tulsa, OK to the Cancer Treatment Center (on of the Cancer Treatment Centers of America) and they were fantastic. I will never go anywhere else for treatment.
I hope I helped answer some questions. I'm only 42, and like you, this was a great concern. Hang in there, and let me know if I can be of any help!
P.S. - The only restriction I have is a limit on my protein in-take. I still have a glass of wine with dinner now and then, and a cold beer still hits the spot. Your nephrologist will be able to tell you about your situation. It sounds like you might be dealing with something a little different than I... keep in touch.