Q - Why was the human wizard Glennnifar kidnapped?"
A - We kidnap lots of people for slaves and food.

Q - "Where have the other's taken him?"
A - Into the caves.

Q - "Who is the leader of the group that turned our friend into a Black Dragon?"
A - Meachan is our leader but it was Agorath that turned your friend into the Dragon.

Q - "Have the others gone to some lair or fortress further up the hill?"
A- Yes.

Q - "Are there any secret or hidden paths up to or into where they are keeping the wizard?"
A - No, just the trail.

Q - "Are there any traps or passwords that we need to get to where they are keeping the wizard?"
A- We dont have any traps or use passwords. You have to get past the others and they will kill you.

Bardic Knowledge will help you identify local notable people, legendary items, or noteworthy places. It can hint at what a magic items powers might be. This wont help you id the potions. Sorry :(

Will you be casting Detect Magic?