Id consider any business you push his way a favor to your current customers. Seeing if he would buy you out of whatever you don't want or your business might be the best way to deal with it and then continue on for a bit like someone else mentioned.

It's a tough situation for sure. It's great to pass on the knowledge but at what point do you stop when it becomes an inconvenience to you. Maybe talking to him and letting him know you'll help out for a certain price is the best way to handle it?