Living with a drug dependent, verbally abusive bf

I am living with this guy who is dependent on some type of benzodiazepine. He used to be able to buy a hospital sized jar of this medicine in the country where we used to live. But when we moved to a country where this medicine is regulated, he could no longer take as much as he used to get. He could only get a maximum of 90 tablets per month, but it only last him two weeks. He would drink for consecutive days up to a week of non stop drinking. He would call me names (bubblehead, stupid bitch, stupid ###$, useless, worst thing that happened to him etc). He would call me his ex wife's name, telling me I'm his wife without the benefits... He would yell at me and blame me for the smallest things like when he can't find the song that he wants to play from his playlist. He would tell me to leave the house and never come back. He held me by the hair and dragged me out of the house in the middle of the night, twisted my arm behind me and pushed me to the balcony at the 36th floor where we live. He would tell me he wasn't too get rid of me so he can bring home and ###$ a girl half my age (we are both 36 y/o). He would tell me that a young girl would be far better deal for him. He would tell me that I'm too old and doesn't want me... But when he's sober. He would tell me that I'm the most important to him, he is caring and sore his love for me.
I'm confused. I feel like wasted whenever he tells me abusive words but I can't leave him. I always feel that I should stick by him if I really love him. But I also feel po or he doesn't respect me anymore by telling me those words...
How would I know when is time to give up on him? Anyone please help me!!!

The time to give up on him was a long time ago. This guy is physically and mentally abusing you. There should be no tolerance for $#%^ like this. LEAVE HIM!

This thing makes me miserable. He gets sick when I'm not with him because he doesn't care about his health. I'm always worried that he might get into trouble or have a road accident. It is very hard to decide... I'm still hoping that he would change and everything would be ok.

Hard to accept but.. why would he change? Just out of nothing? Doesn't work that way..