My first thought would be that since he is getting limited exercise for his body he needs more interaction and "brain" work to tire him out. If it were me I would spend 15 - 30 minutes a night working his mind with basic obedience, tricks, and anything else you can think of to work his mind so he will sleep well at night. My guys would do the same thing if they didn't get their work outs everyday. You just have to do the same thing but with his mind.