SheltieGuy, I can understand how you are feeling, really. My first dog - a Malamute-mix named Candy, died from kidney failure. At the time she died, we were feeding her the IAMS moist chunks (when it was in packets) because she had issues eating dry food because of a maxi-esophagus.
At the time we had her on that food, was right when the issues with the gluten from China was a big issue in MANY MANY MANY canned brands of food. The issue caused kidney failure. Talk about something hard to live with.
Honestly, all we can do is the best we possibly can. Our dear beloved animals are always going to have a risk of getting a serious problem like kidneys, liver, cancer, etc. regardless of what we do. Heck, even in humans people who live near 100% healthy lifestyles still die from heart attacks.
We can read everything out there but sometimes it is possible to OVER ANALYZE that we because unable to make a decision one way or the other.
From what I've been able to gather, the average protein is in the 20% range however if you have a more active dog, you can go higher. If you really want to be safe, do annual or bi-annual blood work with your vet and, if necessary, change foods again. And this should probably be done with ANY food you feed.
Beyond that can we really do much more without giving ourselves an ulcer or worrying into inactivity?