My advice, for what it's worth.... if you can with minimum hassle,move. Because anything else you do could well land you in trouble yourself. Neighbour confrontations never end well. And if you think somehow you are a p*ssy for not knocking him out or whatever, just remember he will end up coming across someone who is just as much as a lunatic as him, or someone with nothing to lose and he will end up in a box or in prison himself.
He sounds like he is wrong, but again ,if he posted his version of events, it might look different. and if it looks different to us it could to the police and the court system, so again, take the path of least resistance and if you can move. If you cannot, say you cannot afford to, or it's impractical, all I can suggest is contacting landlord and also,whenever you feel 'threatened' by him play his game and contact the police. If any neighbour approached me with a gun or a knife, even if it was on hisbelt, I would be straight on the phone to the police,I would be phoning the police night and day until he was took away in handcuffs.And thats another point,from what you described, sounds like he has a mental issue, could you contact social services or something . . You need to play the game here, sadly we aren't in high school anymore and you can't settle things with your fists without ending up in trouble yourself. What you need to do is build up a lot of paper work, police landlord etc etc about him in case it escalates. But this is why ,it's far easier just to cut losses and move.
Say you even go smoke on doors, he will just find something else to whine about,because you are on his radar now.And it's not cowardly to move or call the police in , if you have a job, etc etc, good way to lose your job or fukk up your future career getting into a confrontation with a neighbour,Iam much taller and bigger than dude in question here but the law always seems to side with the scumbag in my country.