In "Just Lather, That's All," what is Captain Torres's real purpose in coming to the narrator for a shave?
Unfortunately, according to enotes regulations I am only able to answer one of your questions and so I have edited down your question accordingly. This is a great question though, and although we are not explicitly told the answer, I think we are able to infer a lot about the character of Captain Torres from what he does and says.
It is only at the end that we are given the "sting in the tail" of the story and we find out that Captain Torres knew about the barber's links with the rebels all the time. This is a shock because throughout the tale the narrator had thought that the Captain didn't know that he was on the rebels' side. The fact that Captain Torres went and allowed himself to be shaved to "find out" whether the barber would kill him shows that he is incredibly brave - insanely so. Perhaps his work has made him love taking these kind of life-or-death risks - they give him a thrill that he gets a kick out of. However, the fact that Captain Torres sat calmly throughout this process and then nonchalantly reveals his knowledge at the end, before walking out and leaving the barber be suggests that there are definitely hidden depths to this character that is otherwise presented as a bloodthirsty, violent and vindictive man:
How man of us had he ordered shot? How many of us had he ordered mutilated? It was better not to think about it.
Captain Torres's assertion that "killing isn't easy" presents him in a more human light and forces both us and the barber to reassess his character radically.