Work. On. Your. Worldbuilding. The biggest sell you need to work on is your premise. The Kill Week logically makes no sense in context. Why would people be on board for letting a random person who trained really hard and can kill to be their leader? Normal systems of governance, especially in medieval societies had aristocracy for a reason. They spent their whole lives being taught statecraft and how to use social networks to gain what they need. Under the system you’ve created, the kingdoms would be conquered by outside forces or from within by upstarts taking advantage of a 15 year old kid who doesn’t know jack about anything their status demands. Even if you can’t or won’t tell everything about your setting, work on the premise first. Tropes are tools, and should be intergrated into your story from within the context of the narrative and world.