Oh no, another of these threads. Maybe I can dig up some short story somewhere to finish and stick up here...
Little: An interesting story, but the first thing that nagged me was its tense. 'He fumbles a book of matches out of his pocket, dropping the can of gas.' is present. 'He looked up, and the glass glinted.' is past. Pick one or the other.
Side rant: Present tense is becoming a cliche. It was edgy back when Snow Crash came out, but now that everyone* uses it the charm is fleeting.
Continuing on, 'and' implies that the two clauses are related and happened in order. "I slammed him in the face and slit his throat as he fell" makes sense, "I built a steam-powered calculator in my fort and Barack Obama was elected" does not. The glass does not glint because Jason looked at it, he happens to see it because it does.
'(which, unbeknownst to Jason, contained a large cylinder filled with roughly five hundred galleons of heating oil)' If we are following the perspective of Jason, why do we get to know thing he doesn't? If the detail is intended as a surprise, why is it here? If it isn't relevant at all, why is it anywhere?
IMPORTANT SIDE RANT: If a detail doesn't help the story, don't include it. The best way to accomplish this is not to add details that don't.
'Cataclysmic explosion'. Adverbs in general. It's hard to do, but it is far far better to have the reader draw the conclusions you want them to rather than dealing them out. Ernest Hemmingway was the master of this, check out The Old Man and the Sea or one of his other works for how to write an entire Pulitzer Prize novella using 'slowly' and (I think) 'steadily' as the only adverbs.
Last lines: I was confused at bit about this, too. Again, it could be a little clearer. Is the reader to understand this is supposed to be the influence of some mysterious telepathic arson thing? If so, I would suggest one of two things:
A) Make it more clear that this influence isn't natural.
B) Set up the story as a mystery as to why an ordinary citizen would start burning down buildings, and fully reveal the arson monster at the end. I know, some how, this can be done without the reader guessing the secret right away, but I can't think exactly how right now...
But in any case, I enjoyed it. Keep up writing.
Impending doom: The passive tense often appears in your writing. The use of it can make your story stilted and clumsy. Sometimes the drama of sentences is lost. This can be corrected. The active voice is better.
Also, is this a finished story? You mentioned unfinished stories above, is this one of them? As it is, the story ends at an odd moment.
The box is too obvious. You mention it at the end of segment and put special attention on it. Why should the reader doubt at all that you intend for it to be a plot point later? If you want for it to be a surprise, you must hide it first.
Anyway, I'm going to stop my critique now, as I have a headache and it's late at night. Keep writing. I'll read the other stories tomorrow.
FINAL SIDE RANT APPROACHES:
Any of you planning a career in writing, or just planning to get any done: Take note. You need to say to yourself 'I'm going to write n hours today'. N can be 1, 2, 4, 0.3, whatever, it's too easy to not work up the effort for a deadline a week away. If you're planning on writing a book (which I did) there's no other way to finish it in a reasonable timeframe.