Welcome Satellites.
What can you do? Well, you can take care of yourself and your needs. Unfortunately, he needs to be in charge of his own life and choices, and if he chooses to drink himself silly every night, it is his right. The anger and defensiveness are normal when an alcoholic is confronted...that will continue. Addicts protect their addictions - it is their utmost priority.
You are young with a bright future ahead of you. Is this how you see it playing out? If not, it may be time to reconsider this relationship's future potential.
When I was a little younger than you (back in the day!) I had to make a similar choice. It wasn't easy, but the reality of my situation was clear. Having a boyfriend who was drunk all the time was more like a noose around my neck than a fulfilling and fun relationship.
Good luck!
~T