The reason Kurn wasn't willing to just wait it out was 1) for plot device and 2) because from his perspective Worf had no reason to fight for their honor. Worf lived a comfortable life in Starfleet, a life not at all affected by his choice to side against the Empire. Kurn's life was the Empire, without it he didn't want to live.
In addition to the ending, I am also bothered by the fact that Worf ever thought he'd be able to carry out the ritual suicide on DS9. Even if he hadn't been stopped by Dax, how was he planning to dispose of the body and account for Kurn's absense? If anyone ever found out he would have been tried for murder. They should have left the station and gone outside of Starfleet's jurisdiction. This is how he got away with killing Duras on TNG, he did it on a Klingon ship.
Worf..he was ultra Klingon-- he took everything literally to the point that even other Klingons couldn't understand him...
Agree. I like to say that Worf is a textbook Klingon, because all he really knows about Klingons is what he's read or studied. Jadzia calls him out on this in "Let He..."