I was stuck in what I believe is the same place. It is when you are leaving, right? Jump onto those two outcropping parts on the right, jump to that little ledge near the corner, get as close to the corner as possible, wait for full stamina, then run, double jump and dash (right mouse) towards the broken rail and you might make it.
If it is right at the start, with the bookcase, that was patched to be non-exploitable. You now HAVE to use your first key to pass that door.
And yes, skipping D2 will make you miss those two H-pics. Probably the harpy girl and fairy as well, though you can just F12 her in later.
Nah not that. I meant THIS MONSTROCITY