Sonnboo, I listened to what this guy had to day, the sound of his voice. The inflections he used. I'm not a doctor and I don't play one on tv but in my opinion, this guy is clearly schizophrenic. He may actually be capable of carrying out his threats, but what is also clear is that he feels empowered by the attention you are giving him. I don't have any advice on a course of action simply because it sounds like it's too late. The wheels are in motion and spinning freely.... Now, just for a second, try to see this thing from the viewpoint of a disturbed individual. You have made a documentary about him, telling the world that he is a monster. Imagine how that might be interpreted by someone who has a clear, yet unfounded hatred for you. He probably does not regard how he has acted toward you, only how you have acted toward him; you are following him around the internet. You are suing him. It's fair to assume that he sees you as the aggressor, someone out to hurt him. If confronted with the facts, he would probably say he threatened you because you want to know where he lives so you can come to his house to kill him.... I don't know... Do you think that's a possibility? Remember, he is clearly sick.
In a way, you are provoking a mentally ill person who, in reality, can not help his condition. Unless he has a support system at home that will help him and make sure he takes his medicine, he will continue to behave as he does until he finally does something that lands him in jail. Maybe at that point you will no longer be bothered and you can then peacefully promote your documentary about him.