What should I do? I need advice from mature people, please.?

Okay...this situation might be a little long to read, but please see it through and help me out, I'm at a loss for what to do. I'm only 16, and I have no trusted adult to talk to so I'm turning to the general public on Yahoo. Please read, and please answer. Thanks :)

Okay, so last night my mom found out my stepdad does marijuana. She'd suspected it for a while, because she'd smelled it on him before but he lied to her and said it was a weird sleeping pill the doctor prescribed him. She found out he lied to her by finding his stash. It wasn't much, and I know pot is illegal for the stupidest reasons, but he still lied to her. His marijuana use proved his double standard, his hypocrisy. My stepdad has called me a drug addict when I take ibuprofen for headaches or cramps, and calls my mom an alcoholic for the glass or two of wine she has every once in a while. My stepdad drinks so much more than her, and he drinks the hard stuff, like vodka and everclear. Though my stepdad drinks and smokes, he's given so much to my family. When my biological father and my mom divorced, I was maybe 5 and my sister 1. He's practically raised us, making sure we got good grades and provided a great private school education for me for a couple years. He's given more to my sister and I than my biological father has. His parenting styles are not much to my liking, I must admit, as he is the epitome of the "authoritarian" parent and often enforces his (frequently insane) rules with screaming, intimidation, and physical violence. I'm not saying I'm beaten to a pulp, but I believe that it's uncalled for and the punishment does not fit the crime. I do love my stepdad, but I don't know what to do. Last night, my mom was crying really hard, and yelled at my stepdad that she doesn't love him anymore and she wished he was dead, she wants a divorce, and we're moving to an apartment ASAP. After their big argument, I went and comforted my little sister, and then went and comforted my mom. My sister fell asleep and then my mom went to take a shower. Right then, I was so out of my mind and I really couldn't stand it, so I got drunk. I'm not proud of it, but I believe some of the things I said to my parents when I was drunk were definitely for the better, and I wouldn't have said them sober. I definitely overdid the alcohol, and began throwing up a few hours later, so I went in the kitchen to get something to eat when I hear strange noises coming from my mom's room. I went to go see what it was and it was my piss-drunk mom, curled up in a fetal position in the tub and attempting to "take a shower" fully clothed when she had taken one about an hour before. I think, that if I'd left her there in the tub, she would have drowned. She was so drunk she couldn't walk or talk. I carried my mom out of the tub, drunk myself, to her bed and laid her there. She passed out immediately, and I figured she'd fell asleep, so I went back out in the kitchen. As soon as I went out, I heard a huge crash and ran back in to find that she rolled off her bed onto the floor and her iron fell on her face. I moved the iron and all other dangers from her area, and tried to move her back on the bed but my stepdad (who I'd been begging to watch over my mom, as he is 46 and I'm 16) finally came in and told me to leave her there, that apparently this is common for her to do. So I left the room, went to my bed and promptly passed out, from a combination of alcohol, shock, fear, and utter exhaustion. This morning, I woke up to my mom coming in my room and asking me what happened to her, that she didn't remember anything and why does she have huge bruises all over her. I explained to her what happened, and she told me the last thing that she remembered was knocking back a couple sleeping pills with a huge glass of alcohol. I froze and then told her that she could have died, that narcotics and alcohol are deadly. I'm scared and I don't know what to do. My mom values my opinion, and she's asked me whether they should divorce and we should move out. I have no clue what to do and I have no adult to ask. Please do not lecture me for drinking, I understand it was wrong. I'm a good kid, with good grades and grandiose plans for my college, my career, and my future. I just need to know what to advise my mom, and what to do in situations like these. If you read all that, thank you so much, I just needed to get my story out, and I need advice badly. Thank you in advance.