Criminals are neither tough nor brave. Those are characteristics of good people. This is probably why handguns are so effective against criminals. Handguns rarely produce physical incapacitation, but they stop fights almost all the time even in the hands of untrained people.
So, capacity and caliber would matter a lot less than the size, physical appearance, muzzle blast, and accessability of the gun. Fear and demoralization are the source of the handgun's "stopping power." Otherwise, it rarely has any.
And yes, fire away in this situation. You are, I believe, "golden."
I believe in a world which consists of America, her friends, and her dead enemies.