He was just trying to figure out who this Gatsby guy really is, but i think it was to find some ladies he can sleep with. Even as dumb as daisy is, she knew that.
In this excerpt Marcus faces the conflict that his father doesn't agree with him. This type of conflict is called "Man vs. Man" It is the most common type of conflict in a piece of literature, it is also known as interpersonal conflict. In a man vs. man conflict, the protagonist, Marcus, feels something different than another character or the antagonist. This is the type of conflict that Marcus faces.
Hope this helps! :)
I think its "Whose" because 'Who's" is shortened for "Who is"