When I adopted Jack, a Cattle Dog - he had some serious dog-aggression problems towards large dogs. Since he also wanted to attack dangerous things like lawn mowers/cars, etc - I invested in a very good electric shock collar. The key to making the collar work is being able to read the dog's body language; and timing. And voltage. Since a Cattle Dog is a lot like a Catahoula - tough and hard to distract once "locked" onto their target - you need to make an impression. And before folks howl about how cruel this is - one well-timed correction is usually enough to stop a behavior for good. It's why they are used in snake-aversion training.
But I'll say this as politely as possible - if your dog is turning on YOU in the midst of its one-dog dogfight; then you need a professional to give you guidance, because you need to assert your authority a little better. If the e-collar isn't giving the message to your dog "Dad just said to sit and ignore the other dog, and I know he's the boss" - an ill-timed correction could actually tell your dog "See???! I just got hurt and if I don't kill that dog/person, it will hurt Dad, too!!!!!!"
And the e-collar never got Jack over his dog aggression - all it provided was the constant reminder that he was not allowed to fight with other dogs and when told to ignore something - he had to listen to me and walk away. Once he was controllable, I enrolled him in our local Kennel Club's obedience class, explaining to my instructor that he was there for socialization. They allowed me to use a pinch collar on him and were very encouraging, even when it might have appeared to the average dog owner that I was pretty tough on Jack. He did great, too. And in his 13 years of living with us - he could run loose with other extended-family dogs and NOT get into a fight.
So I believe that with a lot of effort, consistency, and proper mind-set (not "fear that we'll encounter another dog", but "determination that your dog will listen to and obey you"); your dog can be convinced to be a good citizen.