Thanks for digging and trying to help figure this out. I agree it's definitely in the area. Its just so weird that the IRT would build this tunnel and then cover it up.
There's another video on Instagram with another series of pictures. Unfortunately, I cant link it, but I noticed there were a series of numbers painted on the walls. They look like coordinates or markers of some kind, but I cant figure it out. Could this help pinpoint the location?
24+15
24+20
23+?
26+50
75+15
180+00
I had a browse through the NY historical society subway photograph collection and many of the pictures had the same number convention (station xx+xx). Here is an example of what I am writing about: https://digitalcollections.nyhistory.org/islandora/object/nyhs%3A93278