I think the bans are absurd and should be lifted. If any State thinks its curriculum is getting out of control, it should legislatively enact non-legislative means for establishing better teaching materials--it's more flexible and more applicable.

But your first two points have good answers.

1. You determine intent and impact the same way as you do with any other legislative directive, including, for instance, the directives in the Civil Rights Act. How do you know whether something had racist intent, or racist impact? Well, you collect evidence--is there a consistent pattern, what were the actual outcomes, etc.. There is no difference here.

2. The only thing you need to do to not teach that the U.S. is an inherently racist nation is simply to not say that it is, and also not teach only the racist parts and nothing else (hence giving the impression--that is, you probably can't teach straight 1619 project material and nothing else). Inherent whatever, as opposed to having aspects of whatever, is a hard case to make no matter what the "whatever" is. With respect to racism, teaching (1) that slavery was allowed at the country's founding, and (2) slaves counted as fractional people, but (3) the explicit ideal was that all (men) should have the right to liberty etc. is enough to show that you're not teaching the inherency of but aspects of racism.

The other points are all at least somewhat decent questions and most are difficult to answer well. But these two are easy.