Not an argument.
You say that it should not work under vacuum? It is an incomplete statement, why to make it complete and I will look at it again.
But for now let me tell you that objects that obejcts that are in vacuum still falls down since they are are ore dens then the surroundings.
Anyway you can also just look at the flat earth:
The thing is there is no medium, and it still goes at 9.81 m/s/s. It is all consistent even with an atmosphere if we account for small error of drag. Under your flat earth hypothesis objects of different densities should fall at different rates.
Also a quick analysis of your the video shows that the video is fish eyed and negates the curve, if anything it applies a negative curve to it.