I don't have all the details here but if you do in fact feel threatened then you have to call the cops. But what a cop can do is limited unless you have an actual restraining order or he is in fact committing a crime. They can get him to leave but can't stop him from coming around unless there is a legal order to do so. Just telling someone that they cannot come around is difficult to enforce if you are in fact opening the door and letting them in. Sounds like you aren't there yet but are recognizing his obsession and I'd encourage you to take more definitive legal steps to stop him. Maybe the threat of you telling him you are ready to get a restraining order could be enough but tread lightly and contact people who know more about this stuff so they can advise you. You don't want to escalate the situation either.
