It could be both, maybe they hurt themselves because they want to call some attention or it could also be their way to feel better with themselves
Yes it is a metaphor because he does not literally have a key to her heart. It is just figurative speaking.
A. Gloomy
This is because if you read it, it is definitely not bittersweet. Ravens are signs of death and this is not murderous because no one is really getting murdered, its just the gloomy feeling of not knowing and how it is constantly happening.
