Back of the envelope calculation for energy released by fission bomb based on binding energy?

I read that the strong force is twenty frigging pounds between every two tiny protons. So by multiplying this, say, 10kgs by the number of atoms that undergo fission, do we get roughly the energy released or is the force exerted between protons irrelevant? (I am guessing that only two protons per atom, not all the protons in an atom are involved.)

I think the more direct way of doing it is converting the lost mass into energy via the well-known formula but perhaps we can get a similar number by using the above.