I wanna try to get to a different ending, but instead I keep getting the same one.
Also, how do I open the vault?
the vault should be open if you're at the point where you get that 2nd quest in the mine...
you need to beat victoire before the under the library dungeon to move onto route 2. alternatively you can load one of the saves i included in the zip to access routes 2 and 3, just load them up and exit the dungeon.