Looking for a new home would be fine. . .but what will you do if there are no takers? It's not easy to find a home for an older dog, especially a difficult breed with behavioral problems. I don't think people are going to be ringing your phone off the hook for a chance at this dog. If it were easy to find homes for adult dogs, shelters wouldn't be killing so many. So assume it's not possible to re-home him. Now what will you do?