What is your total completion % in the library?

[dmpdesign]

The boarded up entrance simply requires you to slash at the boards, they should break down when you hit them...so there is nothing stopping you from entering that area very early in the game. ‎  However, you will find without the armor from Thedeck's keep which provides superior fire protection, that the beasties beyond that door will likely kill you in one or two hits, so you do have to sort of wait until the end to go in.

I don thave a good answer for why your verdite boss is not showing up unless the event file for the library was some how an out of date one. ‎  The carrion worm is probably just buggy I will check into that one tonight to be sure. and let you know.