I agree that it is never too late to train a dog. It may just take some different techniques. My very first GSP had been ultra traumatized before I got him. Same type of thing, dog didn't hunt they banished him to a kennel and I got him for free. I really think that the dog (Boomer) was as a puppy thrown in the water, attacked by ducks, and then shot over repeatedly. I had never met a dog so scared of anything. Anyway, he passed away recently but by the timed he passed away he would swim and did better around guns.

It sounds like with this dog, he specifically needs to whoa. I think that would be achievable, you should try a whoa post (Del Mar Smith). I read about them, and if you use it correctly the dog does not associate the pain of the pinch collar with you. Which in this case would help to build trust.

Not that I know ALL that much about hunting or anything, but that is my input. OH, and it looks like from your pic you have a kid, so worst case your little guy get's a lab buddy. I always feel bad for dog's who get kennel banished cause they aren't hunter's.