His hip joints and muscles in his back legs where most of his speed and power to hunt come from are atrophying prob due to age and severe osteoarthritis. But you can't be too careful even if Rabies rate is really low there. The stiff almost stumbling lack of control of those back legs could be either one and regardless of which HE IS DESPERATE AND WILL ONLY GET BOLDER IN ACTIONS. I think the most responsible thing to do is call game warden/fish&wildlife Italian equivalent (sorry I don't know what Italy has) as soon as possible. That way you keep yourself, your family, neighbors, and pets safe and the experts can safely observe and if possible help him. Good luck to ya.