2001 but without HAL, so Dave Bowman is the one to go crazy. Best unreliable narrator I've read/heard in a while. And while we do find him unreliable very early on, I think it adds -- not hampers -- the story. What is he not telling us, and how much of what he does say are lies?
And I like we don't know what happened to the coffee beans. Told 1st person (past tense), if John had found them, it would colour how he told the story: Either "I misplaced them and killed Richard for nothing" or "He did take them and deserved it." This third, unknown option is more satisfying.
Personally, I think he was snacking on them the whole time -- which is why he couldn't sleep at the end -- but was so bat-s**t crazy he wasn't even aware of it. We know from his 3 hours in the head that time slips by for him without realizing it.
Last point: Kudos for character development of Richard. He is the antagonist of the story, told from a bias perspective, but still as well rounded as he could be in a short work: committed to the mission, stressed, trying to be reasonable, scared. He could easily have been a hardboard cut out but I did feel sympathy for him.