Question

How does the electrostatic force exerted by a proton on an electron compare to the electrostatic force exerted by an electron on a proton?

Answer 1

It is the same.
According to the Newton's third law, the force exerted by the proton on the electron is the same as that on the proton by the electron.

Since proton is a much heavier particle, the acceleration of the proton due to the force shall be lesser than that of the electron. (From the Newton's second law.)