Oops, sorry! Seems I missed few words from your OP.
The broom in Overture is used to get fuse for the generator from top shelf.
However, there's really not that much of an use for it since you can get it by jumping anyways...
But if you want some extra fun, you can always poke dogs with it.
I see you were talking about Requiem instead of Black Plague.
Anyways, you are correct. There are only two endings, which seems that you got them both.
But if you are able to find all of the artifacts in Requiem, you get a secret code which can be used in...
...somewhere during the second level.
I'll leave the rest for you to find out for yourself.