My point wasn't to use the prong for corrections in that instance. It's just a better collar choice than a flat collar when it comes to when a dog tries to back out or pull out. Flat collars can choke and injure the dog. A prong doesn't choke and it puts equalized pressure around the neck and not localized like a flat or choke chain. Plus, it would give u better control.
And yes, your dog was threatened (Or else it wouldn't have felt the need to run) and it ended up injuring a dog and a human. Two things which could have been a lot worse and cost u a lot more. Secondly, no, it's not your dog's job to protect you. Sure, it's nice to think they will, but don't assume on it just because it's a "protection dog". Unless you've spent the money on protection training u don't have one. If u want it to be one plan on spending a lot of money to have it trained to be one.
So wether it helped or not (I just didn't tell u what u want to hear) is up to u. Hopefully you learned some lessons. We don't get better when things are sunshine and rainbows. We learn (or at least should) learn from our failures/mistakes.
Here's my take on prongs: I own one for my other current dog and I've used them with other previous dogs as well. I think they're great tools but in the particular situation is an example of their biggest problem. My goal is to build up confidence and to hopefully show her that no, this dog coming at us is not a threat, but with a prong as she would have pulled away in fear the collar would have closed and the prongs would have set showing her that this bounding dog (who is completely innocent and wasn't injured) is something worth fearing.