The walk the line quest was already covered in the LF1 walkthrough, and the LF2 walkthrough assumed it already complete. It's a real interesting find though, and it wouldn't surprise me if there were a few other goodies hidden away that you would only find by not completing all the quests as early as possible.
For the monocle, that part was actually Kehaul. There was a fair bit of going back and forth between the two authors in chapter 7, and it's more than a little confusing who did what specifically.
Are you sure though. I still have a save file with Cindy all the way at LV. 50, with 3800+ SP using the walkthrough's setup and Tyrant Hat, and she can only pull in 64 of the needed 65 thief points on her best attempt. Were you playing the game on the easy setting maybe, or was this from your non-import play? It's possible that non-importers got a bonus to their thievery points, or it could even be that the points don't properly import from LF1. (Who would really ever check, or how would they check?)
Edit: Actually, I think I might have figured it out. The easy setting adds a 30% bonus to the characters stats. Assuming you're on the easy difficulty setting, that's why your Cindy would have that much SP, and be able to complete it at a lower level then someone on the normal difficulty could.