Be careful with savepoints. More precisely - here comes a real spoiler -
some are not meant to be used, some come with traps.
Also, one of the endings becomes inaccessible once you perform a certain action. More precisely - again, this is a real spoiler -
it is the most obvious thing to do after you get the key.
I was going to fix that, but like I said, the level feels very treacherous already, so I thought it wouldn't hurt to hide the second ending really well.