Tried killing everybody... didn't work. Tried bashing the unopenable door in the tavern... didn't work. Tried to find the one trigger to open the door... didn't know where... Anybody has solution? Thanks...

Nice, never thought about that...

I also had trouble with this part and sympathize with the OP.

The game could have done better giving us cues or hints, no doubt, but I'm glad it didn't just hand us the directions. Having to figure it out on our own really does make us think, even though many of the ideas don't go anywhere.

The problem seems to be when there're not enough cues or they're not intriguing enough. In this particular case, I do think there was an absence of cues which then leads to too many false trails and eventual frustration.