I am having 2 main issues with it, firstly the area were the NPC has asked me to go and kill the Dragon is empty, I killed the dragon in that area whilst exploring and now when I go there, Fast travel or walk from Whiterun with the NPC, the quest marker is hovering above an empty space. I have killed 6 Dragons at this area that were flying overhead but none of them seem to be the appropriate one for the quest.
The second issue is that I cannot get rid of the NPC, if I talk to him, he offers me two handed weapon training and that is it, no other options, I can't use the usual command system either. I have tried going to jail, I have tried to kill him, nothing is working, he is driving me insane and ruining every dungeon that I try to sneak through, he has also picked up (somehow) a staff of flames and is currently doing more damage to me than any dragons or attackers I meet with it.
Please help

Also I have a slight issue in that I cannot complete quests that I have picked items up for whilst looting and exploring (ie having not picked the quest up beforehand. I have the quest items in my inventory and have subsequently accepted the relevant quests from the appropriate NPC's but then I cannot hand them in (an example of this is Panteas flute where I found the flute before meeting Pantea)
Thanks in advance for any help/advice given
