Thanks for getting back to me so quickly:
It sounds as if your horse is suffering from nerve damage to the limb, specifically the radial nerve, which is why he can't raise or move the leg but is just dragging it. It is difficult to know exactly what has happened with the shoulder from your description, and I believe it would also be difficult to be able to diagnose the specific problem without performing an X-ray and/or ultrasound exam. If the humerus bone is indeed out of the socket and has been this way for six days, it will be extremely difficult to reduce it back into the joint without surgery. As the bone is out of the joint, the attached muscles contract and shrink in size, making it unlikely for the bone to return to it's normal position. The nerve that is damaged runs next to this joint, and could have been torn during the accident, or could be undergoing compression due to the muscle damage/bone dislocation. This does not sound as if this problem will repair itself with stall rest and bute.
I haven't asked where you are located, but I strongly recommend that you take your horse to a University teaching hospital or Equine clinic for evaluation. If that is not possible, please find a vet who has portable equipment and is able to evaluate your friend at your home. Longer waiting in this type of situation lessens the possibility for a good outcome.
I wish I had a simple fix and answer for you, but your equine friend has a complex problem.
I truly hope you can get him the help he needs!
Thanks, XXXXX XXXXX wish you the best of luck.