CRF and cooking - Question about Salt Substitues

I'm a bit freaked out after finding out that my 17 year-old cat's blood work shows elevated BUN & Creatinine levels. They appear on the low side of high, so hopefully I can gain her some time by switching her diet to one that's beneficial to her condition. My vet gave me a recipe to replace her canned food, but it calls for a salt substitute (potassium chloride). Everywhere I looked on the internet either refers to KCl or "salt substitute, but the only brand of salt substitute I found at my local store was one called "No Salt" which contains more than just KCl.

Can anyone tell me if the other ingredients found in "No Salt" are safe for cats? They are: Potassium Bitartrate, Adipic Acid, Silicon Dioxide, Mineral Oil, and Fumaric Acid.

Another CRF newbie question I had was on dry food. I've been using Iams Premium Protection for Senior cats for about 3 months now. It contains Omega 3 and Omega 6 fatty acids; as well as Glucosamine and Condroitin, which she needs since she has arthritis. The question comes in on the protein content. This formula has the minimum value of crude protein listed at 35%. I believe some of the special diet formulas run up to 25%. Should I be switching over to a different brand?

I truly appreciate any responses to these questions. Tumby's condition is causing me more than just a bit of worry.

Thanks,
TD