From memory running this for 6 (VTT):
1) I didn't tell them which were easy, medium, or hard. But I did give them general hints like "x seems like a more challenging approach than y" or when they were approaching a check that they'd have difficulty on based on the DC vs. their mod.
2) The lodge entrance is on the right side of the building. The arrow was off a bit on the map. They enter into the room in the top right corner of the building. Muesello's workshop is the left side of the building (which they could enter from using the secret door if they know it).
3) I didn't see any. By not telling them the explicit difficulty, it created some situations where more rolls weren't always better with crit fails. But yes, it's easier with more people. The odd thing I ran into was a situation where they got their clues and the last player crit failed. I deducted their point, but they'd still already found everything. So on one hand, the system encourages everyone to try, but it does seem like something may have been missed?
4) This one was legitimately hard to figure out, especially since they don't actually get a chance to intercept the wagon before it explodes. I told them to situate themselves the way they would knowing an attacking was coming but not from which direction and let them decide exploration activities based on that to see how they'd roll initiative. Two set themselves next to the exploding wagon.
