You know, i am not sure if it helps but i have always wondered these issues to be completely one sided (tenant not leaving the premises).
You guys are leaving for your own house. Why not take some time out and search him a home as well, making his life easy as well?
You will be basically helping your own self this way, indirectly.
Plus, you can always talk to him calmly and listen to his side of the story as in why he doesn't want to leave "at any cost". If his agreement is ending soon, then whats stopping him?