You're doing great so far.
A few almost-no-effort / huge improvement bits from me would be all sound-related.
1. Fix the sound of the humm-buzz of the lights. You can pretty clearly and distinctly hear where it loops; this really distracts from the illusion, and almost has the opposite effect that the buzz is supposed to produce.
2. Remove the ambient "Star Trek: TNG Engine" noise from the game entirely. The buzz of the lights will be unsettling enough.
3. The narration of the beginning of the game is great: taking from the original source material was the right call. But the narrator themselves sounds too...ominous and dark. The person should sound...tired. Weary. Like they know what it's like in there, to wander endlessly. Subtlety is the key to the Backrooms anyway, and you got that in a lot of places. I vote putting it in the intro for Classic.