Well, from what I see from it and what I feel is that its ether one of a couple things.
The letter or paper with drawings could be some sort of message that someone is trying to send you through another life. The map/drawings may be a key to something that was unfinished in a past life and the dead man might be you in your last earthly visit,.
Or the letter is from a spirit, and the same with the dead man. The spirit may be drawn to you and is trying to speak to you through your dreams.
The letter may also be a warning of dead, linked to the dead man. It might mean that Death is coming, don't panic, it's probably not for you.
I would suggest trying to recall the things on that paper and writing them down and trying to figure out what they mean.
That one's a bit harder (Thats what she said).
It may just be a strange dream, but I'm not sure. The 'devils' you're speaking of here sound like Shadow Demons, or Ebony Demons. I've seen them before. They are dangerous, but they're not known for possessing.
Again, it may be some sort of a warning or it could be something you're mind is trying to tell you.
Usually injuries to the hand (Like the dog biting your hand) means a feeling of helplessness.
The devils disappearing could mean that something is running away from you, or you're trying to forget something horrible.
The speed might mean that you're feeling behind, and you have problems nipping at your heels.
The flying seems to me like you're getting freedom from something, but you're not able to go very far (hence the limit of flight)
Thats just what I get from reading this. I hope it helps