I’m the son of an addict: here’s my most recent story at 29 years old

I recently moved back in with my grandparents as well as my mother and stepdad. My mom is using again and her husband is doing it too. I’ve been awake for 2 days straight listening to them yell and cuss each other out and threatening divorce (brought back some happy childhood memories with my mom and dad lol)
My older sister came over to offer mom a way to get help for both of them before they lose their inheritance his dad left them on the condition they stay sober but mom lost her shit and started yelling and getting in her face. Now, I’m very protective over both of them and my intention was to deescalate the situation, so I went in between to pull them apart and she punched me in the stomach and I. Lost. My. Shit.

I can’t go into detail over everything I said, it’s too brutal. But I said something along the lines of “You ever put your hands on me again, I will throw you in prison for the rest of your miserable life. Me and her aren’t 12 years old, we aren’t scared of you anymore” Now, I’m almost 6’0” tall and about 280, I’m not a small guy by any means at all and I was rabid and said way worse things than that but I swear I put the fear of God into her. I learned today that I do not have it in me to be a mean person, cause that look on her face has been making me feel like shit ever since. I stepped away for a bit and came back to mom doing the same shit to my sister as she was doing before so I pulled sis away and told Mom “Whatever you think you’re going to do to her, do it to me.”

I told my grandad that by the time I get back from my trip on next week, if they don’t have a plan to get treatment or if they haven’t been thrown out then I’m gone.
The worst thing is, I’m not even okay with my sister either since she punched me in the face not too long ago. Why does my family think it’s okay to hit me? Is it because they know I won’t hit back?

If mom had just slapped me, I can shrug that off because that’s just Thursday and my childhood. A punch has way more to it than that. It’s the principle