Give credit where credit is due
The short story is "There's a Man in the Habit of Hitting Me on the Head with an Umbrella" by Fernando Sorrentino. I can't stress how terrible it is to leave the source of your inspiration out of the credits, especially when it's from a story as famous as this one.
As for the movie itself, I had trouble getting into it. Fernando Sorrentino's stories always seem to play out in my mind as if the weather is permanent overcast -- dark colors and mostly duotones -- not the vibrant brights that you've used. And I'm not saying this just because I prefer the way that I see it in my mind's eye, but because the way you portray it detracts greatly from the mood: if there isn't much going on and the action is all static, then, as a rule of thumb, you don't use loud colors, you use clean, calm colors so that the main idea doesn't contrast with the way that you present it.
I also didn't like the artistic liberties that you've taken with the story. The protagonist never went insane from the poking. But more importantly, he NEVER wanted to kill himself. In fact, he strictly stated in the story that he could kill neither himself nor the man: "I recognize that I would never dare to kill him or kill myself."
So, although I gave your movie a 3/5, I really should have given you a lower score for how far you've strayed from the actual story. And, if it was your intention to set aside the short, at least make it so that we couldn't recognize where the idea came from so that those of us who read the story wouldn't have conflicting viewpoints.
I understand how much effort goes into this, but please make sure that you understand what you're doing.