have to answer the first question myself:
as we know, luchos were physically identical, but the first had way more text chiseled away – so, of course, 2nd was heavier.
Presuming, Moshe was carrying them as in the movie to show to Jews, then the first lucha will be on right side for the people, or in Moshe’s left hand, so the heavier 2nd lucha was in his right hand, corresponding to two ideas above. So, here sevora, gemora, and physics all match.