Why the Binding Energies of Neutron and Proton are different?

In my textbook, Problems in General Physics by I E Irodov there is following problem:

I am able to solve the problem. I am able to do all the maths, to the right answer, but I have a conceptual doubt.

Why is there a difference in Binding Energies in Neutron and the Proton?

Earlier I thought that because the masses of proton and neutron are different, so there is a difference in binding energies. But, the solution given everywhere says something else, which brings me to this doubt.

Following is the solution given in most places.

I do not understand, what coulomb repulsion has to do with the Binding Energy? I always thought we calculate Binding Energy only with the help of Mass Defects, but here the situation seems to be something else. Am I missing something in the understanding of Binding Energy itself?

The binding energy is the energy required to separate the particle from the nucleus.

The strong nuclear force felt by neutrons and protons is approximately the same, but only the proton feels the repulsive force from the other protons in the nucleus. It is therefore easier to remove a proton than a neutron and so its binding energy is lower.

I did some research and found the following reasons.

The reasons for less binding energy in case of proton than in the case of the neutron are the following:

1. Mass of neutron is more than the mass of a proton.

2. When we remove a neutron there is only one force that needs to be overcome - Strong Nuclear Force, but when we remove a proton it is true that we need to overcome Strong Nuclear Force, but at the same time, the electrostatic repulsion force facilitates the separation process. The effort to remove a neutron will be greater than the effort to remove the proton, so the energy required to remove a neutron will be greater than the energy required to remove a proton.

3. The rest mass energy of a nucleus is less than the rest mass energies of constituent protons and neutrons. The reason for this is, the mass of a nucleus is not calculated by the individual constituents alone, but also on the basis of the interaction forces as well. These interaction forces are like - Electrostatic Repulsion forces between the protons, Strong Nuclear force between the nucleons, weak nuclear forces etc. These interaction force also constitute some potential energies and these energies also correspond to some mass, from the mass-energy relation by Einstein.

4. The following resource on Wikipedia gives some detailed idea about how the mass of a nucleus is calculated. https://en.wikipedia.org/wiki/Semi-empirical_mass_formula