The mercenary handbook for single-player mode seems fine. I reached the elite level after killing 4000+. However, in multiplayer mode, I killed 40000 and I'm still at the intermediate level. Sigh.
For the last part, to enter the dimensional space, you need the elite handbook + pass.
The pass drops together with the Silence Ring.
I've been farming all day ~~~~~~~~~~~~~~
Finally, I made it ~!~!