What is the difference between Setting/Staging and the theme in Death of a Salesman?
Setting is the time and place in which a literary work takes place. Staging, however, is much more specific. In the theater world, staging can be several things. First, it can be referring to the process of designing or changing the performance space of a play. It can also mean the visual detail that this process creates--the different props used on stage, the blocking of the actors (meaning where they will stand at each point in the scenes). Because this can all be very subjective, one play could be staged very differently because of the visions of different directions. While setting can be a very broad term, staging is usually much more specific. I have included a link from Wikipedia that looks very accurate to me, and has gone into greater detail than I was able to. I hope this helps!
About the theme of Death of a Salesman: there are several. These can be the American dream and abandonment.
The production I saw on Broadway of Death of a Salesman had very subtle staging. The set wasn't elaborate at all, and since there are many flashbacks in this play, the stage had to be set up in a way that reflected what was happening in the present day AND in the flashback at the same time.