I'm guessing there is one and only one way to play through this and win, and that's boring. :(
Mnope. I played a "pretty pink magicless Disney princess" Elodie and won the war with the power of music and good intentions, while others did it with a "Elody the witchqueen of blood" playthrough, so there are definitely several ways to win. The endings are collectible items, just like the "death chibis". They are difficult to find, though, and you will probably need savescumming a few weeks back to try different skill sets that will allow you to get through the gauntlet of the war to the ending you're after.
And although the moment
any event will happen is fixed, many of them will or will not happen according to your previous choices and skill tests.
I agree the replay value drops after a few playthroughs, but the "decision tree" is quite dense, with hidden branches.
And your first death was exactly the same as mine. That birthday party is for me the moment where things get really dangerous ^^