"omnipotent" might not be the word you want. It means "all powerful", so, not only would they need to be able to rewrite the laws of the universe, they would need to be not only the best at it ever and without limitation, but there would be no room for this individual to improve at their ability.
"absolute control" might work better, if you aren't trying to ascribe literally God-like power.
generally, yes, but "metaphysical", meaning literally "beyond physical", brings in spiritual/etc dimensions that have nothing, by definition, to do with the physical laws of the universe.
My main problem is that people say Time is not a part of physical reality? Is this true? And if so, does that mean it is metaphysical, or something else entirely?
time is product of our physical universe, afaik. there might be other universes with different times, but time in our universe is a physical phenomenon.