But nothing hit WTC7 which invalidates this reasoning and WTC1&2 survived the aircraft impacts just fine

WTC 1 and 2 hit WTC7. You can see they knocked out a full corner of the building, which coincidentally is the side that started falling first, pulling the rest of the building down.

That is actually a sign of controlled demolition because it defies the conservation of angular momentum, if you are to believe the gravity-driven collapse theory

Your detailed explanation relies on this statement:

But in reality, the rotation of the block rapidly decelerated as the downward plunge began

But watching the video reveals that that the rotation didn't stop, the block simply increased its acceleration down, which would have allowed further impacts to break it apart.

How did they prove NISTs theory right?

The experiment in question simply proved that a shotgun could strip away fireproofing, it didn't prove or disprove any theory. Presenting it as proof of a controlled demolition is disinfo tactics, which is why I don't trust your sources.