Try hardening your heart and making him eat dog food. If you think about it, dogs that are treated badly eat wood if they get hungry enough.
Give him dog food, and allow him 15 minutes to eat what he is given. If he doesn't eat it, take it away and don't give him anything else until his next mealtime. He won't starve if there is food offered to him and he is hungry enough.
Also, don't add nicer food to his bowl after you've given it to him, if it's to try and make him eat. He'll learn that if he doesn't eat, something nicer will come along. Give him nice leftovers and treats by all means, but put them in before you give him the food, or after he has finished his portion.
Have fun!!!