If I feel threatened in my car, I am not allowed to run over the person
You are not allowed to run people over merely because you feel threatened.
You are allowed to use deadly force, in the USA when you reasonably believe that it is necessary to prevent someone from unlawfully killing, causing serious physical injury, or committing a short list of violent felonies. The harassment described in the article probably does not rise to that level, though an ambitious lawyer might try to describe intentionally causing the car to stop as carjacking or kidnapping.
He can’t. He’s paralyzed and his exoskeleton is broken.
On a more serious note, the 404media article (login wall) reports the problem was that the wristwatch controller for the exoskeleton had its battery wire’s solder joint break. They seem to be trying to frame it as a right to repair issue, but that’s a trivial repair for anyone with basic electronics experience.