I see the “threat to his rule” as everything in the previous two paragraphs: flames of rebellion, Rey training to become a Jedi, Leia being a force of unity. And the “hidden power” would be the gigantic fleet which on this version is Kylo’s main motivation. So I think the last paragraph nails down everything perfectly to imply this new direction for Kylo’s character.

Changing the “threat” back to Palpatine as it was on the original crawl undermines that direction. Instead of Kylo seeking out a way to quell the growing uprising, a current threat to his rule that ties directly to the previous film, he’d just be searching for rumours of a possible threat to his rule that has nothing to do with the current affairs of the galaxy. And it goes back to Sherlock’s previous worry of spelling it out to the audience Kylo wants to take down Palpatine instead of keeping things ambiguous.