It isn't known. A proper difference between people of the same level with different stats has never been given. All we know is that the one with higher stats is stronger, but it has never been said by how much.

Unknown. Probably not as we do get in fact stronger when he pass from being kids to adults even the strength of an adult is nothing compared to a person with falna. Though, being too old can affect overall performance.

If you are asking if points have the exact same value between all species, yes they do.