I feel that the story's discursiveness is because it's in the third person. In third person writing, the author generally assumes the role of a story-teller in its most distilled form — the author will detail a plot and the events surrounding that plot as comprehensively as possible. In my opinion, it's a clumsy and out-dated way to tell a story. When writing short stories, there's often a constraint on what, how, or how much you can write, as unsignedinteger notes. Therefore, for short stories particularly, the author should put consideration into leaving bits open to thought and discussion; otherwise a couple of sentences or a couple of pages are left as a largely forgettable experience. Consider the extremely short story (sometimes mis-attributed to Ernest Hemmingway): For Sale: Baby shoes, never worn. That's quite poignant and whilst some might argue that it leaves a lot to be desired; I feel it leaves a lot to be contemplated upon.
Above experimenting with writing about new emotions, political agendas, sentence structure, and so on, I'd recommend writing in new perspectives. Write stories in third-person, or first-person, or alternate between a whole cast of characters' experiences. You might even want to experiment with more contemporary developments in writing such as stream-of-consciousness or epistolary stories. One should do this so that the author's interaction with the characters is different and so that the reader's interaction with the characters is different. Someone reading a story that's a stream-of-consciousness is burdened, perhaps uneasily, by the fact that what they're reading is a total exposé of the absurd complexity of the human thought process and the banality of many everyday observations that enter our cognitive ambit. An author writing in the first-person for example, must uphold a certain standard of perceptiveness for how the character would act in a (their?) situation.
Just to exemplify this point of narrative person in relation to what you've written, you write: "“A car can’t travel faster than radio waves, can it?”" You've jumped into the first-person to intimately detail the thoughts of this boy; but at some point here I felt you'd become lost between wanting to describe the boy's thoughts in detail and wanting to take precedence as an omniscient, dictating writer of third-person. You describe the boy as smart, but that is not to say rational. At the time that he thinks this, he's driving to this girl's house to uncover what has happened for emotional catharsis. Constructing a thought is difficult in what are apparently harsh conditions for your protagonist, so how would he construct this thought? Well, what is a text? A text is a text. Whilst that may seem a redundant point to make, it's an axiomatic, safe, and easy conclusion. So when thinking under the pressure that I feel you're trying to convey, your character would be much, much more likely just to say 'text' (and by doing this, you'd have separated the boy from the author to a further extent).
Obviously this isn't a comprehensive assessment of what you've written, but I hope it's food for thought.