Written material seems to imply that Starkiller Base is capable of traveling through hyperspace. Like Hal said, with the way Restructured is cut, it is not necessary to have to speculate on that question in his version.

Yes, draining a system’s star basically dooms any planet that exists in it, but it’s not a really effective method of genocide if the people on those planets can still evacuate their world.

I know Star Wars is pretty fast-and-loose with the science in science fiction, but there are definitely more uninhabited star systems than there are systems with habitable worlds, so it’s not like they really have to choose a system to sacrifice in order to destroy another. There are literally billions of stars in the galaxy to choose from.

Sure, they totally could doom another rebellious star system if they wanted, but they don’t have to.