Gatsby is desperately searching for someone who knows Daisy. When he finds out from Jordan Baker that Nick Carraway is Daisy cousin, Gatsby latches on to him in an effort to get Daisy back. Everything he does is for Daisy.
It is probably murder, because the word is most commonly thought of as being hateful and full of unbridled emotion, and in this particular passage, it is most likely used to convey disgust.
C, An approaching storm would be a foreshadow of something bad happening
