Hi there! Yes, you found the spot to ask a case question!
Normally, when a blood-borne pathogen is associated with the development of renal disease, then the problem from a Chinese medical point of view is Shao Yang disharmony (i.e., a deeply penetrated pathogen causing persistent systemic immune stimulation and inflammation). Perhaps that was true at one point and now it is resolved, but usually resolution only happens with herbs or acupuncture.
If you'd said the pulse was Wiry or forceful, that would have been enough for me to recommend Xiao Chai Hu Tang as the first formula to get going. To make sure that is not the right way to go, can you get a urine protein:creatinine ratio done? If it's well above 3, then the case is still a Shao Yang disharmony, making Minor Bupleurum (Xiao Chai Hu Tang) the place to start. Many severe aggression cases are Shao Yang dogs, and they have strong appetites because of the tendency for their Yang to get trapped in the Yang Ming, leading to Stomach Heat.
If the UPC comes back below 3, then it's a deficiency case, I guess. Given the pale to lavender tongue, weak pulse, azotemia and strong appetite, the dog most likely has Yin deficiency. I would address that with Yi Guan Jian (Glehnia and Rehmannia) or Zhi Bai Di Huang Wan (Anemarrhena, Phellodendron and Rehmannia).
Kan Essentials makes versions of all three if pills or liquids are easier to give than granules (like Natural Path). The Minor Bupleurum you'd use from Kan Essentials for the kidneys is actually Benefit Hips and Knees. Zhi Bai Di Huang Wan is sold as APR Nourishing.
Hopefully this helps you out!