Enotes does not allow you to ask multiple questions, so I have been forced to edit down your original questions to just focus on the first one that you asked.
As in the majority of works of fiction, Jack London employs a variety of different examples of figurative language to help aid his description and establish his theme of the innate frailty of mankind in the face of the vastness of the power of nature. You might want to go through the story again and identify each example of figurative language and consider how it builds on or develops this central theme of this powerful short story.
For example, one powerful simile describes the man and his skills at observation in the treacherous terrain he is trying to transverse:
Once, coming around a bend, he shied abruptly, like a startled horse, curved away from the place where he had been walking, and retreated several paces back along the trail.
This shows the one time that the protagonist of this short story acted instinctually (like an animal or the horse he is compared with), but at the same time he is acting on his knowledge that springs often lie under the snow and a thin layer of ice. Lacking the instincts of the dog and the good judgement of the older man who warned him about the dangers of travelling in such cold conditions, he is still at the mercy of nature.