MY only real advice would be to move out of the house regardless of what the chap may do. Go to your Gran or a friend and take a few days to sort yourself out.
Find another room to rent within travelling distance to work and begin thinking about looking for work in another area. It sounds as though you are stuck in a rut with little chance of ever improving your situation until you change something.
Take no notice of the GD "man up" nonsense, it is a horrible and frightening position you find yourself in and antagonising someone as unstable as this chap appears to be will not do you any good if you are not physically able to defend yourself, walk away. There is no shame in that whatsoever, and I expect most of those saying it would fill their pants just living in the same house as a drug addled, unpredictable and violent house-mate, let alone getting threatened by one. Don't go and 'offer him out' hoping he is bluffing, he may well not be and it will only make your situation worse. Real life is not the Karate Kid I'm afraid and unstable, unpredictable people are rarely balanced enough to be afraid anyway. Leave him alone and start moving anything of value out of the house as soon as you can.
Treat this as an opportunity to drag yourself out of the situation you are in. Remember that as soon as you are out of the sight of this fool he is likely to forget about you in short order, his self hate will focus on other things more immediate to his vicinity and if he is saying that he is going to get others to hassle you, it is because he is a bully who is afraid of the consequences of doing it himself. People who are genuinely hard don't talk about what they are going to do, they simply do it.
I don't know where you live, but as hard as it may be, changing your life situation seems like something you want and need to do. Use this jerk-off as the catalyst.
You can PM me if you want to vent or if I can help answer any questions, feel free.