I am so sorry for the situation you find yourself in, no one should aver be treated that way. It is extreme emotional abuse, and the stress will not be healthy for your unborn son. He is clearly a man of low character, violent, and an alcoholic so will not be a good father. His behavior will not change until he gets completely sober and works a long-term plan of recovery, which is different than just getting sober. It involves work on character. He belongs in AA.
I agree that you need to get out of there and to a safe place. Contact a domestic violence hotline when it is safe to do so, for more guidance. Do not tell him where you have gone, leave when he is not around, and do not go back - as that is when these types of men are most dangerous. I also suggest that you read a book on co-dependency and more of the threads on here.