Planning out your meals is going to be the deal breaker. When you are in areas with easy access to stores, you can buy perishables in smaller amounts and more often. For the "long stretch" through Northern Ontario where you don't have easy access to stores, plan meals using non-refrigerated foods (spaghetti with jarred sauce, canned corn, bread, etc.). Then go back to the perishables when you again have easy access.
Carry snacks that don't require refrigeration - crackers, chips, fruits, etc. Save the fridge for mealtime foods (meats, etc.). Freeze milk and use it in a cooler to keep other foods cold - as it melts, drink/use it for cooking.