It's normal for you to feel like this, there is a lot of pressure on you especially because you're expected to continue studying, qualify and get a degree.
People (especially in the line of work you're into) are very harsh and apathetic, but it's nothing you can't get through. People above you will always be intimidating but it's part of the process, you need to build ambition and concentrate more on getting to the top than being put down by those on top. Make sense?
You wont get a job? Can you prove that? Dude, you need to open up to opportunities, you will definitely get a job, but you need to be open to the idea, meaning don't just say "I won't get a job, for sure." rather say, "I'll make sure I get a job."
Your state of mind is to blame for how you feel. And I believe you can alter your state of mind- you just need the will to do so. And trust me, I'm not giving you "false hope" I've presenting logic to you.
Doing drugs and smoking stuff is just going to make things worse, you need to keep clear headed in order to prosper. Give up on the drugs and smoking, no matter how "lightly" you do this- just stop before it's too late.
As you would know, humans are social creatures and I would say that you don't need friends or support system- but then I'd be lying. You just need to find the right people and trust me, that will happen. Even the creepiest, most introverted types have someone. They may not be too close to that someone but they DO have someone and you will also find a friend/partner/guide to help you get through this difficult time.
Assess your thoughts properly and you will surely find a way around this hurdle of negativity.
FINALLY: DO NOT KILL YOURSELF, don't down those pills, don't pull that trigger. I can tell by the calibre of your question that you are smart enough and strong enough to control your thoughts and thus get through this difficult stage of your life.
I did not spend close to half an hour reading your question, giving it a lot of thought, and typing this just so you can ignore my advice and give up okay. :)
Been through something similar.