No prong! That is exactly the wrong tool to use as a rookie! It can put drive into a dog not take it out! And if as you say he does not respect you he could very well "come up the leash on you" if you use a prong badly on him! Right now your best bet is to manage him, keep him away from the other dogs put a drag leash on him and or a muzzle. Keep the other dogs safe have him checked again to see if there is something medically wrong with him.
Two or More Dogs
Your dog has to respect you as a leader for any training/leadership to work
Leerburg Dog Training | The Groundwork to Establishing Pack Structure with Adult Dogs
Good info here about dog aggression in general
Leerburg | My dog is dog aggressive. What can I do about this aggression?
It sounds like you most likely need to find a competent qualified trainer, I had this problem myself with my GSD he had no problem with me running the ship but he wanted to run the crew!