There are many foods manufactured by Diamond. Chicken Soup is actually part of Diamond, Natural Balance, unless something has changed, is not. Honestly, you'd have to ask the dog food company for a copy of the certificate from the manufacturer of the fish meal that states whether or not the fish meal is ethoxyquin free.
As for the protein levels, I personally feel that people are a little too nervous over this issue. Unless there is an underlying medical issue, high amounts of meat protein are not an issue. First off, consider this: For a 70 lb dog, depending on metabolism and activity level, approximately 2 cups of Orijen (42% protein) would be fed. The same dog being fed Chicken Soup for the Dog Lover's Soul (24% protein) would eat approximately 3 1/2 cups a day. If you break it all down, you aren't going to find huge differences in the amount of protein per feeding between the two. What you will find is that by feeding Orijen instead of Chicken Soup, you will be providing more meat protein. Not only that, you will be cutting out a huge portion of unnecessary carbohydrates. Not as great as a raw diet, no doubt, but certainly far better for a dog than a grain laden food that is low in meat protein. Don't even get me going on the carbohydrate issue.
Kidney issues can develop on any food. No matter what kibble you offer, it is still kibble, still an unnatural food for a dog. If you feed a high protein kibble and your dog is even slightly dehydrated (not uncommon with kibble fed dogs) the test results for kidney values can be off. They can also be off if the dog has not been properly fasted prior to blood work.