Get a lawyer to help you. The laws for restraining orders/protective orders are different in every state. Where I live, they're extremely difficult to get, and in your case, a judge wouldn't even consider it.
What you can do is talk to people, as you have. Tell your landlord your X is an alcoholic and that he's only looking for a place in order to create problems for you. Tell your friends that he's stalking you, and advise them to tell him to bugger off if he shows up again. Even if you can't get the law to help you (and frankly, an actively drinking A might not care an awful lot about a piece of paper saying he can't go to "your" dogpark), you can smack doors in his face with the help of friends & family.