Your original question infringed enotes policy by asking more than one question and so I have had to edit your question down to just one question. This is the kind of question to be honest that you can answer either way - as long as you support your response fully. The text gives us no clear indication so you need to think about your own personal response to the barber's decision to not kill Captain Torres and think about whether it is correct or not.
Personally, I think at the end of the story the barber experiences a kind of epiphany that means that he has a moment of realisation about himself and his place in the world. He realises who he is and what he is and is not capable of:
But I don't want to be a murderer. You came to me for a shave. And I perform my work honourably... I don't want blood on my hands. Just lather, that's all. You are an executioner and I am only a barber. Each person has his own place in the scheme of things.
Thus the barber realises something fundamental about his identity - he is a barber, not a murderer, and therefore he makes the right decision by being true to who he really is and not killing Torres. In return, Torres himself comes to respect the barber for who he is, just as it seems the barber respects Torres and the role that he plays.