It's not just the main cast, NOBODY named dies from a sword or knife in the entire series, to my knowledge.
Mind you that's not because swords/knives are nonlethal in universe, it's just a funny quirk of the series. Dedicated swordsmen exist to get chumped out in Naruto, and knives are exclusively used to reposition people for more effective attacks. It's part of the charm.
Two points here, one minor, one kinda nitpicky.
1.) Zabuza TECHNICALLY expired from knife/spear wounds...after he was already stabbed through the chest with lightning and had both his arms paralyzed by enormous dogs fighting Kakashi. He then basically committed seppuku by killing a dozen guys with his ****ing teeth and making little to no effort to dodge their attacks so he could beeline Gato. Zabuza, specifically, only died because of a combination of being too weak at the moment to properly defend himself and because he WANTED to die anyway after he realized he really did care a whole lot about Haku.
2.) There are several "ranks" between Jonin and Kage. Jonin is a leadership rank that denotes a certain level of skill, and is sort of the highest OFFICIAL rank (though Special Jonin is above that, even), but there's a wide gulf of strength between your average Jonin and a Kage and there's Special Jonin, village specific superheroes like Sannin, S-Class Ninja (most of the Akatsuki fall here) and the catch-all "Kage level ninja" for people who can 1 v 1 manfight a Kage in their prime. Jonin, yes, is the rank just under Kage, in sort of the same way General is the military rank just under the president (with the same nuance that a one star and four star General have vastly different levels of authority).