Hmm, I would think the "behavior" he was sent to the principal for is related to his disability: "socially lacking because of his 2e-ness of autism spectrum." Schools are required to determine if behavior is related to disability through a manifestation determination, when there is a potential "change of placement." This is usually the 10th day of suspension or a change to homebound or whatever for behavior. This process also requires them to determine if the IEP was appropriate.
But this really sounds like punishing him for a disability. That's a major no-no.
I think I'd pitch a fit at the IEP. You can write a parent statement of concern that has to be included.
I agree with bringing your psychologist but I think I'd try to find a sped advocate, too.
Good luck!! It's so frustrating!!
