Indexical traces of difference

1. Does the yellow portion of the following context about Andy Warhol's art make sense to you? Does it mean his artworks appropriate ready-made images and represent them without changes from the original images, therefore, his art is similar to a machine that takes images as input and represents them without any changes as output?

2. Does "whose proximity to death" apart from the electric chair, skulls, and car crashes, refer to "Marilyn Monroe" as well? Does it imply that Andy Warhol's artworks representing this actress were created after her death?

3. What does "blanket" mean?

4. What does "indexical" mean in "indexical traces of difference"?

Context:

The artist whose life and work are not only synonymous with the conservative strand of the death drive and Freud’s notion of the desire to return to homeostasis, but which also expose the dynamic of repetition compulsion is Andy Warhol. Warhol’s art practice epitomises the desire to control the death drive by imitating the mechanical operations of a machine, whose input and output are equivalent and which lacks tension. The content of his imagery is often derived from images of death in the media – the electric chair, skulls, car crashes and movie stars like Marilyn Monroe, whose proximity to death made them seductive. He subjects these images to a blanket serial repetition, albeit including subtle differences caused by the glitches of the screen-printing process. However, these indexical traces of difference are minimal.