I've had several cats over the last decade. Some were bigger cats, some were smaller cats. My bigger cats needed more food than the smaller cats.
Without knowing how much George weighs now, and if he is underweight, overweight or ideal weight will help determine how much food he needs. So, current weight is? Underweight? Overweight? Just right(ideal)?
No, I would not leave the Orijen dry food out overnight. I have no idea which of the many types of Orijen foods you have, but most of those Orijen dry foods are 25-30% carb content. Yes, it's grain free, but they have replaced grains with all sorts of peas and beans and lentils which increases the carb content quite a bit, making them too high for a diabetic. Remember, you are looking for foods that are <10% carbs, >40% protein.