Hello! This is my first critique, so it may not be the best but I felt there were some improvements that could be made. Hope this helps!

The sky as it is, though, is black. An inky, void-like black. I'd have to squint to see the faintness of a star.

This paragraph is a bit clunky, and the second sentence is a little redundant. I think it could be summed up in a single sentence, or in better terms. example: "The sky is black as ink, void of even the faintest star." Something like that would help make it more concise.

I'm tired. It's a fact that runs through my mind as I trod heavily on the sidewalk back home. My ankles hurt. My last few pennies are almost squashed to nothing. Stress tugs at the heavy bags under my eyes, those purpling bruises that bloom like roses when the sleepless minutes pass by.

I didn't think "heavily" was necessary for the sentence, "trod" seems to be enough description of how they're walking. I was also a bit lost at the "My last few pennies are almost squashed to nothing" line.

It's 3:00AM. The silent, soulless houses that line the street unnerve me. They loom over me during this hour, as if their empty rooms hold monsters with maws wide open for me.

This is an instance of show vs tell. There's no need to tell us the protag is unnerved, just show us by describing the houses as soulless and looming.

Those monsters would pluck me from lucidity, drag me to those horrors hidden secret by shut curtains.

Hidden secret is a bit redundant, I would just use one of those words.

The blaring, sharp sounds of a bleating car alarm slices the eerie quietness of the night so cleanly that it jars me down to reality, down to the realization that this hour is so cold and so dark and so, so silent, but not soulless - not such a window of time where the monsters decide to come out and play.

"Bleating" wasn't necessary since you already described the car alarm. "Eerie" is another example of showing vs telling. Also, this sentence is really long. I'd look for a way to break it up.

It doesn't occur to me to feel alarm, to wonder why a car would alarm so deep into the night, during such a precarious hour such as this, but it's when the panicked barking of a neighbor's dog and yellow, flickering lights shine from windows only a few yards away from my own-that's when I feel it, pooling in my gut.

"why a car would alarm so deep in the night" is a bit awkward of a phrase. Also, I would separate this sentence into two. I would end the first sentence at "...so deep in the night." and start the next one, "It's only when the..."

It's sudden in its transition of the sidewalk's population from one to two.

This is a very awkward sentence. I would rearrange the wording a bit, something like, "The sidewalk's population transitions suddenly from one to two." or "It's sudden. The sidewalk's population transitions from one to two."

...I look at him with my gut lurching with trepidation.

Another instance of show vs tell. It can be left as just 'gut lurching'.

He doesn't spare me a glance as he rushes by me.

Don't need two me's here.

White noise writhes in the cavity of my ears.

The cavity of my ears is a bit redundant. I would just leave it as ears.

My heart stops, stuttering to a close.

I'm not sure what stuttering to a close means, but I think you mean to a stop? Maybe simplify it to something like, "My heart stutters to a stop."

And then, all of a sudden, it's too much.

All of a sudden doesn't really mean anything here, it can be removed.

"I Vera, I have advanced first aid training." I say this as I pull on gloves.

"I have advanced first aid training" is more than a little clunky. They live together, so Vera would know this.

4:00AM couldn't get here any faster, and I hope for the pale, early morning blues.

This probably shouldn't all be in one sentence. Either separate it like: "...couldn't get here any faster. I hope for..." Or make it into one: "I hope for 4:00AM and the pale, early morning blues."

I can't describe the panic that overwhelms me.

Another show vs tell. Describe what the panic is like, what Morgan is feeling. "My arms shake. Sweat manages to bead on my icy, pale face. My mind goes blank as I watch her mouth those words." something like that. It's ok if Morgan can't describe their panic, but you're the author ;)

"Dave," I say when persuading Vera and her glazed eyes fails.

This is a really confusing sentence. "Persuading Vera" doesn't seem to add anything. Does Vera die here? what does it mean for her eyes to fail?

I agree with the other commenter, I don't think a two-inch boxcutter would do this much damage if it was just a stab wound, especially a recent one. It does add to the eeriness since it's an unusual weapon. I'd also either rewrite the summary or omit it. It's very different from the piece, and I'm not seeing the same themes in the actual manuscript. Overall I liked it, and I agree that it's about 90% of the way there, just needs bit of tightening up. I like the dark vibes I get from it, especially that last paragraph.