He's a brave kid, no question about that, and he did exactly the right thing pinning the dog and choking it because 99 times out of 100 a dog will submit when it's pinned by the neck because that's how fights between dogs are usually settled.
I used to work for an animal charity training and rehabilitating dogs and I'd think twice about getting into a fight with a pit bull because I know from experience that anything bigger than a border collie can do you serious damage. The worst fight I got into with a dog was with a rottweiller bitch that attacked me because she got a little freaked out when I entered what she considered her territory. She didn't have a collar on at the time and to be honest I'm not sure I could have pinned her so I had to kick her in the jaw as she charged me to stop the attack. The remarkable thing is that despite getting kicked square in the jaw with a heavy combat boot she wasn't injured but the shock and pain was enough to turn fight into flight which was lucky for me as she would have ripped me to pieces if she'd managed to get her teeth into me. I think the whole thing was over in less than a minute and once I'd calmed her down she turned out to be a very gentle, affectionate and good natured dog but because of that one attack she was deemed too high a risk to re-home and she became one of the kennels permanant residents.