This is not my subfield so I may be talking out of my depth, but it feels like you are conflating two different concepts. There is a physics assumption that law

This is not my subfield so I may be talking out of my depth, but it feels like you are conflating two different concepts. There is a physics assumption that laws are universal, then there is a cosmological assumption that energy distribution after the Big Bang was (near-)uniform. Dark energy and dark matter follows mostly from the physics assumption not the cosmological one. Do you have a cite for the galactic spin thing?