Starshine, I think you are already doing everything right. Keep it up and after a while he will understand. I don't allow food thrown on the floor here either and pick it up and show it to them in my hand while saying 'not on the floor' 2-3 times with my mad face and stern voice.

It might be a good idea to remove balls from play for a few months until he catches on to that rule. I do have balls mixed in with my toys and allow them to be thrown or kicked in the toyroom but the rule is they have to be kept at knee level or lower. The children climb onto my couch where they play a lot but the window is behind the couch so I'm reminding them not to stand on the couch a lot. We have a lot of fun here but safety is always #1.