Ask the pirate if he knows what the note says.
"Hey, this looks like professor's handwriting!"
"Professor?"
"Yeah, Professor Collins. Me, him and a few others went on this expedition to explore the Void, but we were caught by the mushrooms and locked up here. In fact, I think that Professor was in your cell."
"It turned out that the mushrooms' spores affect our mental health by... well, they just make you go bonkers. At least that's what Professor said."
Ask pirate about his bandana.
"My bandana? Well, I just thik it's cool, that's all. Even though it makes people think that I'm a pirate..."
Use the club to widen the hole!
Seeing as how your last few acts of violence ended, you don't really believe this'll work. But still, it's worth a shot.
Damn.
Then give the powder to the pirate guy and tell him to use the spark from his lighter to ignite it and blast a hole in the wall. You hope it's flammable, anyway.
"I'm sorry, but that won't work."
"And how do you know that?"
"Well, there are several problems with that idea, but I'll just say that this isn't gunpowder. Though... Gimme a sec, I'll try something out."
He walks away from the hole, still holding the flask in his hand. A second later, you hear him beat on the door of his cell. Looks like your discussion has come to an end. You'll probably have to start actually doing something.