Again, you are misunderstanding it, it's the uniform pull of the plane. The infinite plane is what forms the pull in the first place.
The equation above has the density of the plane itself factored into the gravitational pull. All areas are part of the same uniform plane. It's not like point mass gravitation.
And I already answered that question, the normal unit vectors and gravitational cancel out on an infinite plane, making it stable. These vectors are infinitesimal.
Please be patient, the last time I touched advanced math was 20 years ago.
The equation above has the end result of
g being a function of density. If the density is higher,
g will increase.
In more layman terms, are you telling me that if I bury a neutron star in my backyard nothing will happen?
According to your objection, on a spherical Earth, more dense areas will have greater gravitational pulls and less dense material will be pulled away. However, we know that the gravitational pull across Earth is a product of the entire mass and not particularly areas on its surface, as those all form the uniform mass of Earth and therefore it's uniform gravitational pull.
You can consider earth a point when calculating gravity, because it's a frickin' sphere. However, if you were to dig down, the gravity would decrease, as the earth above you pulls you "up". At the center, you would be de facto at 0 g.
Furthermore, we have slight variations of g due to different densities (
https://en.wikipedia.org/wiki/Gravity_anomaly).
So no, there's nothing uniform in there.