If the charges between a proton and an electron were not exactly the same all the matter in the universe would repel all the other matter, and so the universe would expand, just as it is believed to do. The trouble with that idea is that yes, the universe would expand, but -- short of extraordinary special dispensations - it would not do anything else. Even so small a difference in electric charge would be enough to overwhelm the forces of gravitation that bring matter together; and so we should have no planets, no stars, no galaxies.
The same for the sizes of the particles and the distance between the particles. If they were slightly different the universe could have been created in the exact same way but would be devoid of life. The structure of matter and energy are literally tuned for life.