Matter expanding in universe-questions

When the universe expands what part of matter expands? Is it the space between the nucleus and electron/protons, or their size? If the size of the nucleus electron and proton increases is there also a size change at more elementary levels?

How could the relative strengths of the elephant vs. the ant remain the same with this expansion? The ant can lift many times its own weight but the elephant cannot. What does this tell us about what we think of as constants?

Since the expansion of the universe is accelerating the effect on matter would be the same as what we experience as gravity. The power of this force would depend on the amount of acceleration. If we would assume that this is the only source of gravity what would the rate of acceleration have to be to match the observed strength of gravity?

Does this match our measurements of the speed by which the expansion is accelerating as calculated by cosmologists? How do you factor in the fact that the measuring devises are also expanding as is the observer?

Could there be a separate size dimension that gives us a constant back drop to measure all this against?