Puzzled over "The Martyr"

"The Martyr" left me with a few questions, and I was wondering if anyone else noticed the same things. On pgs. 35-36, the narrator hints that Ruben's friends know the "true cause of his pain," which does not seem to be Isabel, which he himself does not know. What is this about? Is Porter hinting that he is really not grief-stricken over Isabel, but that something else could be the cause of his pain? In a strictly psychoanalytical reading, could it maybe be his shortcomings as an artist which he uses Isabel as inspiration to conceal?

Also, the end of the story left me wondering about Isabel: what happens to her, her reaction (or lack of one) to Ruben's death, etc. I wonder if Porter is purposefully not giving us closeure on that one to make a point or merely because the main thrust of the story was about Ruben and not her.