I am an avid hunter and have gone through this stage with my boys. Your points above are really good. All I can add is that NOTHING can substitute for taking the time to not only explain these rules, but to stay with him and be sure they are demonstrated. For instance one of my rules is that the gun is to remain on "SAFE" until you are ready to fire, remove the safety and then fire. Once you have fired you immediately engage the safety. I would stand with them and we would practice this over and over as they shot. Out of the blue I would ask one of them for their gun and immediately check it to see if the safety was on. If it wasn't, all shooting would stop and we would go back over our safety rules and start again. Over time the rules became ingrained in their memories and in their habits. Another great rule my father taught me is to always assume a gun is loaded. I know it is a BB gun, but if he learns to treat it like a high powered rifle while he is young, he will have the proper respect for all firearms as he grows.
The final rule I had for my boys when they were young is all guns are locked in my gun cabinet unless I am home and I am with them. As my boys have grown I have allowed them to shoot their 22s on our shooting range, but I still insist on being home. We live in the country on 15 acres surrounded by farms. I know that young men become enamored with shooting things and only proper supervision will teach them how to do so safely. Without supervision young men tend to get a little overzealous and begin to shoot things they really shouldn't.
On a parting thought I might also suggest that you enroll your son in a Hunter's Education course. I realize he may not be interested in hunting, but the skills and safety techniques taught are very valuable. Many fathers enroll with their sons and make it a father son event. I am not sure of your son's age so this suggestion may not be valid.
Just a few thoughts from my experiences.