Since you are feeding mostly commercial foods, you want to keep unbalanced foods to no more than 10% of your dogs total daily calories to avoid nutritional imbalances.
Here is a site I use to find calories and other nutritional info on food:
http://ndb.nal.usda.gov/ndb/search
This is a download you might be interested in that I follow (C4C uses it too) for adding fresh foods to my dog’s diet. You can find these foods at your grocery store. Things like beef or poultry hearts, liver, sardines, eggs, and vegetables. You can make a meal of them or use them as toppers for a few meals. It provides a menu with amounts to feed according to your dogs weight and the kibble you are feeding. I add them as toppers rather than feeding in one meal. I always suggest this download to anyone interested in adding raw or lightly cooked foods to a kibble fed dog. It is an easy read with lots of info:
http://www.dogwise.com/ItemDetails.cfm?ID=DN330EBK
