Good Job! The only thing I would suggest is if this ever happens again, call 911. First to cover your arse and second to get this nut off the road. If you described the incident to a dispatcher it does a couple of things: creates a record for you, ie the police often go by the unwritten rule of the first caller in a confrontation / fight is the victim. Second should a police car spot him driving erratically away from the area at a high rate of speed after your call, you can bet he's in for a felony prone stop. Something this guy needs in my opinion, as it is just a matter of time before he hurts someone, if he has not already?
On another note, just because you drove away from this dirt bag does not mean he is not a threat anymore. He could of just as easily drove after you down the road and watched for a chance to ambush you. If he did and you were forced to dispatch him to the nether world there would already be a record of you trying to get help to keep him away from you; clearly making him the aggressor and you the victim.