MANPADS are certainly covered by ITAR. It could probably be effectively argued by his lawyers that what he has created isn't truly MANPADS but rather just an edgy toy that superficially resembles a weapon system but isn't actually capable of performing as one. Maybe that would work, but I think his chance of getting dragged into the legal system for this or for some chickenshit like weed possession are very high, particularly if the media at large picks up this story.

https://www.law.cornell.edu/uscode/text/18/2332g states that just having a system "intended to launch or guide a rocked or missile described in... [description of MANPAD type rocket]" carries life imprisonment. He calls it a manpad and then shows a system intended to launch it.

There is no consideration in the law whether he actually plans to use it or ever meant any violence, nor any consideration of whether it violates ITAR.

As someone who has a lot of interest in weapons law, this is probably about the only kind of weapon that can't be even legally contemplated in the USA, worst case for almost anything else you can get an NFA stamp. The USA is absolutely paranoid about yielding their air power so they come down like a ton of bricks against anyone that might want to defend against that.