Lea,
I am ACOA (adult child of an alcoholic) and witnessed alcoholic insanity and abuse at the hands of my father and codie mother that are beyond horrific.
Insanity becomes "normal" and we never learned how to have healthy relationships as they were not patterned for us. Out of 6 siblings all of us struggled with relationships, married addicts or became one.
The good news is that several of us got counseling and pursued recovery for ourselves and got better and have broken the generational passing of the torch of dysfunction for the next generation and hopefully their children will not experience what we did as kids.
Fortunately you are an adult and you have choices and are pursuing information on addiction and relationships with addicts.
I can not offer you much hope with what you have told us. Untreated alcoholism (he is not pursuing authentic recovery) is not pretty and it is progressive. His ACOA issues will not go away without professional counseling and processing his "automatic" reverting back to what he witnessed and experienced as a child and is hard wired into his personality.
He CAN change. BUT... only if he wants to and with a LOT of very, very hard work in counseling and true recovery. It is unlikely that he will pursue this path especially if he is under a lot of stress with school etc, etc, etc.
But... you can pursue your own recovery and get involved in alanon and make your own plan A and plan B. Alcoholism is the ultimate in uncertainty... have a plan of escape in the back of your mind... you will most likely want to pursue it at some point.