For the record I am not buying what Cornwall says about relativity.
It is logically independent from his quantum argument.
Entanglement signaling if it exists need not be faster than light.
It can be timelike as well as spacelike.
The space-time interval between sender and receiver measurements is completely arbitrary.
In curved spacetime, global intervals are not unique - they are path dependent - although one can look for geodesics connecting the sender and receiver measurements.
Entanglement signaling, slower than light, faster than light and even backwards in time depends on the contingent conditions of the apparatus, delay lines for light for example.
If one used entangled quantum dots for example, you have even more latitude.
David Kaiser describes this to some extent in his Hippies book in the context of the 1982 Chickering letter to DOD.
Entanglement signaling is topological, i.e. non-metrical and there is no need to change Einstein's theory of relativity (both special and general).
Einstein's relativity is based on light signals and it is correct as it stands.