My advice - time for a lawyer or a bulldog of an advocate.

I have a friend who was totally banned from her child's school - not allowed in the building, could not call, could not email. She sold her house and moved to another district where they confirmed everything she had been saying about her son's disabilities. Turned out he had an auditory processing disorder and the first school would not even test him. They were very good at getting rid of "problem parents" by doing exactly this.

I think you will either need to "go legal" to get his needs met here or change schools. I would NOT even consider signing a form like that without input from an attorney specializing in special ed!