Was Edward like the others at the orphanage, an orderly? I suggest that he was brought there as a baby, and probably doesn't remember his parents. And the jar of hearts... it was probably given to him for one of his birthdays. He just wakes up one day and there's a jar of hearts on the table or under the door, and a letter next to it.
Did he work to become the manager? Or did they make concessions to him?