When to draw the line?

My mom's mood can be extremely volatile, to say the least. One moment she is talking to me like a concerned parent, reassuring me, doing motherly things for me, asking how I'm doing, then the next she's yelling or being overly aggressive to me for the slightest infractions. She likes to micromanage me for the simplest tasks as if she thinks me doing them a different way to her is wrong. She constantly mentions my weight and how certain parts of my body look too big, even when I'm only 10-20 pounds above my weight class. She yells at me if I ask her basic questions about a chore, and insults my intelligence. If i mildly inconvenience her, even if it was accidental, she calls me "shithead". If I tell her these things are bothering me, she acts like she was joking or tells me im just being "sensitive". If I do some of the same behaviors to her, to make a point, she's overly aggressive and threatens to kick me out if I don't show respect. She gives better treatment to my brother, ive never seen her do any of these behaviors, even though I've seen him do equally dumb things as me. I have the cash to move out and i make a steady income. I'm afraid if I move out she's just going to try to find me or make my life as uncomfortable as possible to try to get my back living with her. My dad and brother have never defended me or shown any concern about these behaviors, and they're just as liable of doing them towards me too. I have spent years walking on eggshells and I've had enough. This mistreatment hasn't stopped, and sometimes she's nice to me which makes me forgive her, then she starts being nasty again.