My mom and stepdad are fighting! :/?

-Hi, I'm worried and would like some answers :'( please read all the way through

I'm 12 years old and this morning I woke up to my mom and stepdad screaming at each other, I don't know what it was about but my guess was financial problems. My mom kept yelling "I don't love you, I want a divorce, I don't care about you!" at my stepdad. She told him it was all his fault that our life is the way it is. They have been married since I was about 6, but they've been dating since I was 3. My mom divorced my biological dad when I was too young to remember, and he moved to Washington, I've only met him once. I think of my stepdad as my real dad, I mean he is! A father is someone who teaches you how to ride your bike, or who checks your closet and under your bed to make sure there's no monsters, and he's done all that! I'm taking my stepdad's side, my mom's blown-up a bunch of other times over the course of their relationship, and they've all blown over in a few days. I talked to my stepdad and my mom's caused him to have a severe case of depression, he doesn't blame her, but he feels like he doesn't have a place in this world, if my mom left him he wouldn't have anywhere to go, he's too old to get hired anywhere. He's been having thoughts about suicide, and if he did that, I would never talk to my mom ever again! It sounds terrible but she's caused me some serious emotional and physical stress! I lied to her about eating my breakfast, and she grounded me for a month, another time I lied to her about where I got my skirt (she doesn't like me borrowing friends stuff so thats why I never told her) and she grounded me for another 2 weeks. She said I disgusted her and didn't talk to me for 3 days. Sometimes, I honestly believe she doesn't love me! She's also a huge hypocrite, I went shopping with her and she said we spent way too much money and that I had to take all my stuff back but she bought more than me! And then she said that going shopping was my whole birthday and I wasn't getting any presents!! If she divorces my stepdad I don't want to never be able to see him again! But since he's not my dad I won't be able too! :( What do I do!!!1. Ask your step dad to formally adopt you.

2. If your parents got divorced, you could then choose to live with him if you wanted to.

3. Your Mom sounds like my wife. A nutcase. I'm sorry, but I have no advice on that.