You are right, 7 times a day is excessive. My first question has to be how firm are the stools? The Hills should produce a fairly small well formed, firm stool. If it is soft or poorly formed, he has a digestive problem. Whether the stools are a problem, you should have him examined by a vet and discuss the problem. It is possible the Hills is not the right chow for him. Despite what you may read in some places, most dogs will thrive on most diets, but there isn't any one diet best for all. The solution might be a special grade of Hills, or since it is lamb based, a chicken or beef formula.
This could also be a behavior problem. He may showing you that you can't control his bowel movements. If so, you need to give him better leadership. The key to most behavior problems is approaching things using the dog's natural instincts. Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog. Life is much easier if the 2 legged pack members outrank the 4 legged ones. You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at
Raising Your Dog with the Monks of New Skete For more on being top dog, see
Establishing and Keeping Alpha Position, Letting your dog know you are the boss