So many questions..

I personally think that he would try to start a new life. Why? There would be no point in going back. Scar's crazy but he's not stupid. His character is described as scheming, intelligent and manipulative. I think the events that lead up to his death/exile would really phase him. I think he would realize that there would be nothing left for him in a place where he is hated. It would be an even stupider move on his part to try and take revenge on Simba. So in the end, I believe he would try to start over and live what life he has left.