Someone please explain "R" for me

My intake of this segment is that the person strapped in the hospital bed is a film director which produce 8mm genuinely under he's skin, the films are a public success and people adore the "film maker". Every single segment of cell is sugecally removed, he's body is now giving up, he cannot take it anymore and escape the hospital.
I guess the director of this segment found an horror/artistic way to describe the make of a move, the director give himself totally in body and soul during the process of filming ( here is transfigured as literally the 8mm coming from he's skin) some director find difficulty in procure original horror movie likeable to the majority of the public, (we see part of he's body stoping producing the film) the director is try to escape the conventional film horror Hollywood dictators (now the patient "director"escape the hospital o get away by train try to go on a different way. It end that the director won't stop making horror movie but won't be held prisoner anymore by horror standards (we see the blood rain at the end symbolising isn't the end of the horror making movies).