W.O.
Dear L.,
When my son was about the same age, he did the same thing with biting. One day I had enough and I bit him back. He looked at me with huge eyes and I calmly responded, "Now you know how it feels when you bite." He has never bitten anyone since and that was 20 years ago. So go ahead and give him a good pinch - he'll learn quickly. It may sound like an old-fashioned remedy, but it works! Raising my kids, my philosophy was, "Don't get mad, get even," and I did. Now in their twenties, my kids remember a Mom who never got angry, but whose consequences were brutal. And they respect that to this day.
Good luck, W.