My hat is off to you for trying to help this dog overcome his fear.
You may want to visit or call a wolf rescue for tips. Mission wolf has a dog that reminds me of the dog you are describing (except the abuse). From my contact with them they are very helpful and open you may want to contact them directly. The volunteers do not have access to the phone all the time but do go into town to the office from time to time. I know someone is supposed to be there this afternoon.
"Leo is a tall, lanky, goofy malamute who was severely abused as a puppy. When his owner couldn't afford the vet bills, Leo was then surrendered to a shelter, where he was labeled a "wolf-dog" because of his long legs and big head. Since he couldn't be adopted out, Leo was given to Mission:Wolf in 2006. Since his arrival, Leo's behavior has shown that he has very little wolf ancestry. However, since he is officially a "Wolf-dog," Leo will remain at the refuge, happily living with Luna." Discription of Leo by Mission Wolf. He is gorgeous by the way. Would love to see photos of your dog.