Why is my low functioning brother having meltdowns for so many hours daily

If I were to combine the amount of time he has meltdowns daily, it'd be well over 4+ hours.

I am so fucking done and exhausted. There is no end to this. My nerves are so fried having to listen to him scream so loudly.

I am not autistic nor neurodivergent in any way, so maybe you lot can help me out a little here. He's just been screaming non stop for so long continuously. This is NO way to live life. On top of that, he's extremely violent - he has banged his head at my nose and scratched my arms hard.

It feels like my brain is going to pop out of my head due to the severe psychological distress he's given me. If I hear someone shout, or a door bang loudly, I actually start crying because it reminds me of him.

Edit: maybe instead of downvoting me, try sympathizing with my situation. I am literally at my wit's end and extremely distressed, and I thought who else could help me better than autistic people themselves.