OK, I have a few thoughts for you as well.
Back to the basics...You've chosen a reveal from an outside viewpoint to show the problem within your world. Skrune has been murdered and this is how. (but not why, I might add) Then there are a few vingettes from the school where they wonder who is going to get Skrune's orb, and then (as I remember it) Chloe is the viewpoint for most of the book.
This parallels Harry Potter, where the story starts with an infant Harry being delivered to his new home. (Not something that he would ever remember) Then the majority of the story then flows out from Harry's perspctive.
I contrast this with what I remember from the book, Heidi. The MC is informed that her new home is with her grandfather and shipped up to the Alps to live with her grandfather. I don't remember a talk amongst adults in the beginning.
So you're debating the layout of Chloe and feel that the story flows better from Skrune's death.
Good points: It lets us know the stakes.
It lets us know that the world has magical critters
It lets us see the limitations of the orbs.
Bad points: It makes us expect an aggressive world when the first book is more of an adjustment to the new life as a Preases. The dwarf threat doesn't come into play until maybe the last half of the book (if I remember correctly)
It takes us out of the YA 'softer' reality and has a man running for his life and then dying.
It has nothing to do with the first third of the book other than affecting conversation.
This said, I wonder if you would consider having the beginning of your book start with picking up the orb. It is the formative moment when everything about Chloe's life changes. It keeps the momentum but doesn't have a big reveal about the overall plot. That leaves us to learn about the world as Chloe does. As well as the threat (which she is unaware of for most of the first...eight chapters)
Just thoughts. Hope they help you put your choice about the first chapter in perspective.
A