I have much empathy for you, OP. I had 3 of my 4 children with behavioural and learning difficulties and another one with more physical and medical issues. All adopted as babies. All with ASD. Now they are adult we are foster carers for children with complex needs. So obviously we have been through much of what you are going through. If my experience taught me anything is that every children is unique, my twins needed different approaches, and no one size fits all. I also have to say we only ever came across one good EP, the others, well less helpful shall we say.
However, with my son who has similiar issues to yours, I took him out of school to home school. This was because he would scream and cry and disrupt the others in the class, and it was so not fair on the other 29 children who often had to be marched out of the class for their own safety, sometimes several times a day. And also upsetting for him. Although the school were great at trying to manage my son's needs, I realised this was impacting on the education and well being of everyone else in the class. So after I withdrew him I then compiled my own EHCP. bypassing the school completely. When this was refused I appealed and eventually my son was awarded a place at the most brilliant special school that he thrived in and loved. He was young enough to be helped. And although as an adult he still has severe issues, none of them are behavioural and he has never been violent since the day he left the first school.
Some years later we fostered a boy with quite similar issues, only of course there was little we could do as the local authority had parental responsibility. He therefore continued in the school to the detriment of others, and in fact (in his case being quite bright) he was able to turn this to his own advantage. This went on and on. One day he attacked several members of staff and was therefore excluded and given a residential placement in another area of the country. From what I have been told he continues this behaviour in young adulthood, and I have often thought if he had been taken out of mainstream at an earlier stage, if things would be different for him.
How much is covid impacting on the school/staff.your child? I ask because when collecting one foster child from school (mainstream), the children who needed a 1:1 or indeed any "hand on" support, were helped by TA's in full PPE. From the outside it looked quite scary and I did wonder how it was affecting the child themselves - and if it was scary for them also. I think teachers and support staff are in such a difficult and potentially dangerous situation now, and of course although dreadful for the children, how can they help a child calm down at a distance or in PPE. It must be awful for them.
So I wish you good luck and if I had one word of advice it would be to home school your child and apply to TPTB for a EHCP - maybe learn about specialist settings and once YOU have decided which school you think may meet their needs, then direct the EHCP with that in mind. It wasn't easy but I did it, because when you are fighting for your child you can achieve great things. Good luck.