Can you get a copy of the rest of Fred's blood work and post the results, with the lab range in brackets next to it? Also, was a urinalysis done? That's a vital piece of the puzzle (urine specific gravity in particular). If there was no urinalysis, I would make an appointment for one, and add a urine protein creatinine ratio test as well.
I would cease and desist with the K/D. Absolutely atrocious ingredients and there is no valid reason to feed such a protein depleted diet to an obligate carnivore, who actually needs MORE protein as he ages. Instead, find a few different brands/flavours of a good quality MEAT-based wet food with little to no grains and reasonable amounts of phosphorus. There are a couple charts on the net that can help you with that: