Absolutely agree about you needing specialist support, but here are some ideas based on my time as a TA in an EBD (as it was in those days) primary school.
The children I worked with thrived on things being as black and white as possible. No grey areas - if it was wrong, it was always wrong. Well established routines, for example, all pupils sitting up straight at their desk (a double table per individual child with gaps in between each one so no one was sitting close enough to touch another) with their arms folded on the table in front of them, to show they were ready to learn, before the teacher started to teach.
As much predictability and stability as possible in what everyone did. Simple structures which were adhered to like glue. Well do I remember the day the teacher decided to take the class to the hall for an English lesson (she was super experienced and had deliberately chosen to do this) - several children couldn't cope with the change of surroundings - I remember one slid to the far side of the hall and span in circles, which she explained to me was because he was uncomfortable in a different space.
Football was banned because it just caused too many arguments and fights!
Very clear system of rewards. After each break there would be time to review with each child how they had done in the previous lesson and break time against their individual targets, giving them a sticker if it was agreed they had earned it. This meant the day was broken down into chunks of about an hour - if they missed getting their sticker for one chunk, it was clear they could get the next one.
Now this might not be considered good practice anymore as it was nearly 20 years ago. But for those pupils it was absolutely what they needed at the time as any kind of uncertainty unsettled them and put them into fight or flight mode.
Some years later I had a very unsettled year 1 class who I'd been told would need lots of child initiated learning because there were so many summer born boys who weren't ready to cope with sitting at desks. I tried. I really tried. But when those summer born boys spent their whole time chasing each other round the room with guns made out of Duplo, I had to change tack. Clear routines and expectations, lots of very short, age appropriate tasks and structured play really helped them to settle.
I wonder whether your pupils would also thrive with this kind of approach? Include all the sensory activities, PSHE, emotional regulation activities etc in their day as this will be really important to them. But take away they need for them to use their lacking self regulation/executive function by making as many decisions as possible for them. Happy for others to disagree with me!