About falling into the void: It happened to me in the following way: during one of my first playthroughs I tried to open a chest while standing on it. It pushed me through the wall and trapped me where I couldn't come back, so I jumped into the void to respawn. I think it's in that small room with treasure and a spike trap.
I didn't mention that because I'm fairly used to these sort of bugs and since they don't "break" the game I don't give them much attention.
Also, there's a lone barrel in the storage area that you can walk through, it was probably an oversight.
EDIT: Regrettably, I can't figure how to get other endings. Will there be a walkthrough of sorts, even if just tips as to how change one from another?