I agree with Keista...this is off to me in many ways...
It sounds like these continual social issues have some degree of his not perceiving things correctly. The impulse control is obvious but it sounds so much more...maybe it is because of the nature of posts here... hard to describe it all. I can't remember how long ago he was diagnosis but have you considered a new evaluation through a neuropsychologist? Things for most of us change and evolve over time, as the child matures and the true nature of, and the impact from underlying issues happens.
If they are doing a manifestation determination it is supposed to be because they are looking at a behavior or pattern of behaviors that have added up to 10 dismissals from school in the year.... so they need to document that it is a pattern related to his disability. OK sounds like they are already saying it is and they want him in a different place... So the decision from that is yes or no and if it is a manifestation then the team is to look at what is going on... they are to do a Functional Behavior Assessment, discover the triggers, antecedents (including the medication issue by the way), what the specific problem behaviors are, what happens after and the point is to figure out what is driving the behaviors... lack of skills? (need to learn more social skills including non verbal communication which sounds like he has an issue with), a need for something...food, attention, help, peace, a break..whatever... , a need to escape things that are too hard or too easy and he is bored......they must look at slow triggers and fast triggers. They need to consider the environment and how they can modify things, support him in transitions when all these behaviors seem to be happening. Until they do that, to put him in a more restrictive placement just because they don't want to do the hard work is not fair UNLESS you feel he is suffering there and would do better in a setting like that. There are many steps in between that if they have not tried... they need to do to show they tried to keep him in the LRE Least Restrictive Environment.
THAT is a totally different issue. A unilateral change of placement (meaning the administration wants the change and the IEP team has not done any part in going through all the options, figuring out if the IEP goals need to be modified and writing a PBIP that is improved and addresses the problems happening....) can only happen if he committed Serious bodily injury (did anyone have to go get stitches or a cast? any blood?? even a bite is not necessarily serious bodily harm especially given in self defense...serious bodily harm is actually specifically defined by the federal IDEA 2004 so they can't just use their opinion) or his bringing a weapon or his having drugs/doing drugs in school.
So, absolutely have an advocate, and at the very least a witness. YOU have say in where he goes and if residential or whatever this is is not a good fit in your opinion then say NO. You are part of the team. I am going through this too... it is awful but doable!
So, while this is not a complete list a couple of things I would do are: Call an advocate and ask them what to specifically do right away and follow their directions. Really tell them this is an emergency because some advocacy agencies will not show up unless there is something serious and THIS IS SERIOUS....It does not sound like the are following "due process" which they can get in a lot of trouble for.
Then.... put in writing a request for a functional behavior assessment. If it is close to his three year re-evaluation or if there are any areas you are worried about (autism, sensory integration, learning disability, ability, motor, whatever you think) add that too. Then say you want to revise the IEP to reflect current behavioral concerns, to write goals to address the skills he needs to do better and that you want the Positive Behavior Plan updated to help teach him to use more adaptive behaviors and to have support in navigating the social setting he is in. (you can include frequent breaks, a special pass he can use when he is feeling triggered to leave a class for three minutes to do deep breathing or wall push ups etc.... but this has to be TRAINED so not just put in without a method to teach) He may simply need an aide to be with him which is less expensive than sending him to a more intensive and restrictive school.
So, two separate issues. Your son does not sound like he has the skills to do better and like he needs specific teaching/training to learn .... not necessarily more punishment and consequences for not handling situations better. Not saying it is ok to hurt people but to be effective in the disciplinary approaches.... if these suspensions and getting rid of kids would work, then he likely would be fixed by now, right?
My best to you...
Look on writeslaw website.... there is a ton of information on unilateral change of placement and manifestation determinations.