With our chronic kidney animals (Shane the greyhound and Sam the cat), both of whom lived 4-5 years after diagnosis, we learned not to go too low too fast on the protein. To do so makes their other systems suffer and leads to faster deterioration. Shane passed in 2016, but we had used Royal Canin Renal - Medium Protein very successfully with him; then they changed the formula designations to A, B, C or whatever, so I can't tell you what it's called today. Whatever brand you choose, try for medium protein limitation rather than drastic, which is for later in the disease progression.
We also learned that it's the quality of the protein that matters more than the absolute amount. So lactose-free milk was great, and he gobbled up Costco rotisserie chicken!
Wishing you all and your dogs the best. It's a roller coaster, and there's usually an Up after a Down, so keep the faith.