Is there an Incompressible Unit that is used in all theoretical astrophysics calculations?

I guess I don't buy the "Point Singularity" argument that is so often used to describe "infinite density" from which other calculations are derived.

For example, would a neutron, with a diameter of about 1 femtometer be incompressible? Or is a neutron made up of incompressible subatomic particles?

I think I'm now understanding that if you set your event horizon at say 1 attometer, it doesn't take much mass to create a "black hole", whatever that would mean on an attometer scale. However, is it even possible to compress a neutron or a proton into the size of an electron?

Perhaps part of the answer would be whether or not atomic nuclear sizes follow a cubic (cubic root) progression from Hydrogen or Helium up to Uranium/Plutonium/Americium. Can we even measure it accurately enough to know?

(sorry... the progression of volumes to diameter or radius would be a cubic root, rather than a cubic progression).