aggressive over food/treats

Question
I have a 4yr old, neutered, male, black lab. He sleeps in a crate in the basement at night and is outside during the day. I feed him at night when he goes into his crate. I love on him and pet him when I put him in. The past couple of months he has been growling at me if I pet him on the head or go below his ears while he is eating out of his bowl or a treat. I'm sure he is protective of his home/area but it really bothers me that he is being aggressive towards me. Is there anything I can do to get him to stop being aggressive while he has food? Also, do you have any tips on getting him to stay in my yard and not run the neighborhood?

Answer
Dogs really don't like being petted on the head.  It might be better to pet him elsewhere.  Try only starting with part of his food in the dish.  Once he finishes it, add more.  He will soon welcome having your hand near his food dish.  

Most of what I know about dogs I have learned in a program that forbids letting them run loose.  My best answer for keeping him from running the neighborhood is to never let him loose.  

If you can't fence your yard, keep him in the house except for walks or short breaks tethered.