I'm just starting with this game.
According to the rules, the boss fight is like a normal fight. But since I use the adventure die for his hit points - do I still roll a die and add it to his attack/defense values?
Has the boss special abilities, like the normal enemies?
You don't roll the die for his attack/defense, you use the values written next to his HP as they come. No special abilities apart from the fact that if you don't defeat him in 3 rounds, you lose the game.