However, if it stands that the AL SCOTUS can nullify the US SCOTUS, then any state SCOTUS can nullify ANY US SCOTUS decision they disagree with.
Not necessarily. The Alabama SC decision is rightly based on a strict originalist reading of the US Constitution while rejecting the current trend of judicial activism of SCOTUS.
Alabama is merely refusing to join SCOTUS in granting itself powers (legislative) outside of those rightly apportioned to the judiciary.
Courts have no right to change law or create new laws. Period.
Doing so usurps the role of elected state legislatures and the US Congress.