Gravitational attraction is a function of both objects, so the force between them is not a constant, same as for the electron.

Also, what if you have a charge so high that the electrical-escape velocity exceeds the speed of light? A strange kind of black hole?

I ask these things because I do not understand why gravity is called "not a force", while electromagnetism is, when I see no real difference between how particles act.

the link mentions that it's not proven that intertial mass and gravitational mass are the same, they are related. If gravitation mass contributes to the majority of intertial mass it would look like they're the same.

But let's just say they are the same, then gravity and "spacial" inertia are intertwined. Gravity is only special if intertia is also considered special. Inertia seems special because it's explainable in terms of motion in space. There might be other kinds of motion in other dimensions that could explain the randomness of quantum space.