Everything that happens to the Bard at night is narrated to everyone.
Question and answers
How much defines everything? lovers pick? the player that chooses the bard for its ability?
Any active nighttime ability that requires a target to be chosen will trigger the bard, if the bard is chosen
Would abilities that do not require to select the bard [such as sulphuric stench] still be informed to the bard?
No. The bard has to be chosen by an active ability
Do you tell who killed the bard?
Not "who" but any attacks towards the bard will be narrated. So wolf attacks or an assassin attack would be indicated separately. The town can use the bard songs to decipher how he died.
Does it get announced that the bard got targeted, or that, for instance, player 3 got targeted?
No, all "songs" will be in the format of "The role X targeted the Bard", with the exception of the base werewolf attack, which will be described as just "The werewolves attack the Bard".