The way I see this (because I've seen this with other students), his ED is coming from the CPTSD he experienced due to the IEP team not understanding ASD (and his other diagnoses) & not being able to meet his needs. Unfortunately, you do not have the credentials to dispute their diagnosis. In your shoes, I would disagree with the eval and request an IEE at school expense. IMO, he needs a team that better understands ASD & can better meet his needs. You can ask for teacher training in ASD if you feel this is what's going on. You can start by writing a parent concerns letter stating that the appearance of ED is due to the school team not understanding him & how ASD affects him. Without the support like he had in 6th grade when the team did a better job meeting his needs, the lack of support is coming out as behavior which looks like ED.
Is the school also saying that he no longer has ASD? The way ASD is defined includes this: "Autism does not apply if the child's educational performance is adversely affected primarily because the child has an EMOTIONAL DISTURBANCE." If they remove the ASD diagnosis, then he won't get the support he needs at school for the ASD issues.