Physicists Just Learned Something Major About the Proton.

A “four ton force” to pull a single quark out of an atom is not something that can happen. Simplifying a whole lot, the strong force is the only force that gets stronger with distance (up to a certain distance, anyway). Due to confinement, there is no such thing as a single quark alone. Quarks when “pulled” out of an atom form a quark-antiquark pair due to the energy used to achieve this. In other words, quarks can never be alone due to the fundamental nature of the strong force. (This is absurdly, vastly, simplified but is the gist.)

By the way, most of the mass of atoms is due to the energy of the strong interaction, not the intrinsic mass of any particles in the nucleus.