It doesn't matter how saber is spelt outside the US because the question isn't about a normal saber, it's specifically about Star Wars and it's spelt as lightsaber in every country.
A niche is a small recess to hang or display things, or a comfortable area, which can also be used metaphorically to mean an area or field in which one is comfortable
I believe all of these types of quizzes are supposed to be cyclical, so the first letter of the first clue should be the same as the last letter of the last clue.