No he did not make any shooting motions in regards to shooting schoolThere are certain children, at a fairly young age, and heaven knows there are all sorts, sizes and shapes of 14 year olds, who become such a problem to the schools that they simply cannot be disciplined and dealt with within the scope of the normal public school situation. And in my experience this is a very large scope with some very far ranging alternatives. So he is also banned from any school or any sort of alternative programs in the whole county?
I have known of children who have actually carried in weapons or fought with teachers and resource officers who didn't get this much of a total expulsion. It could just be this particular school system. But from the sound of things, we are getting an extremely spotty and sanitized version of this. I really doubt that your 14 year old said anything like, "Please remove yourself from my personal space at once, sir." And when we hear that you "can't find an attorney that will go against Lyon County" that is an indicator that others who have heard this story may have found it convincing enough that Lyon County is within its rights to ban your son. Of course you can always check with more attorneys.
Is it possible your son was making "shoot up the school" type threats, in addition to "standing aggressively?" Instead of fighting against the ban, wanting to demand services for your son from anyone unwilling to provide them, I think perhaps you should use your resources to explore homeschool options and more professional counseling for your son. When you say he has become very "co dependent" I would ask, co dependent upon whom? If he is clinging to you he is obviously needing more help with his issues. It's doubtful that being banned from the school has caused these issues though it may have worsened them. If it is someone outside the family, you need to help him find distance from this influence.