It sounds like you need to get a lawyer, OP.

You're reporting the kids who don't stand up for your kid too? That's insane and that's why no one will take you seriously

What more did you expect them to do?

This happened to my nephew, and all through elementary school it was basically ignored because they “didn’t have proof”. Fast forward to his first weeks at a very large public middle school: turns out they had extensive cameras in the halls and common areas and captured bullying incidents pretty much instantly. There were suspensions for the kids who had been bullying him for years and it got better. The vice principal was p-ssed at the bullies and made it his mission to find it at his school and stomp it out. So much respect for him because many administrators find it easier to look the other way and avoid difficult conversations with bullies’ parents.

Wish I had advice for you. Friend went through this a couple years ago with her kid. Unfortunately I think she made so much noise that the school stopped listening to her and taking her complaints seriously. I think reporting and complaining about the bystanders was what tipped the scales. I tried to tell her trying to get the kids who didn't stick up for her child would probably backfire but she still used their names in complaints.

Ultimately she decided to switch schools

My middle school son has been bullied a lot at school mostly because of a motor tic. It didn’t go away with med changes. Counseling hasn’t helped much so far. We reported bullying many times. Whenever there were screenshots, those were sent in. Physical bullying was reported to LE when it occurred outside of school, and the school was notified afterwards, because other students were involved as participants or bystanders. I was really shocked recently when I requested some paperwork from the school. Instead of addressing bullying, incidents of bullying were referred to as perceived bullying. My son and his parents (us) were described as perceiving that he is being bullied. This is a small district and we complained about the bullying to the superintendent and got a short generic kind of response back. My son has said not to bother moving the complaint process a level up because he thinks it won’t fix anything.
Schools are supposed to be teaching students about accountability but they won’t take any responsibility for their own actions or for inaction when there are complaints about bullying.