Rey you took a dog from proven protection lines and then socialized, exposed and raised it properly and, from your description at least, you now have exactly what you were looking for. I would add another thought to what your trainer said about dogs socialized off leash. The good ones get very, very confidant and comfortable with people.
I believe Derryl wrote
"the dogs talent is recognizing the trainer is not a threat" That is exactly what you get with a good stable dog that is raised right, Confidence! Have you heard the saying "Beauty is in the eye of the Beholder"? In PP terms it might sound like this "Stress is in the heart of the dog" if the dog is very sure of himself, what your trainer is doing to push him into "defense" just may not really mean much to the dog.
In the Security Dog industry we have a saying, "You can only train with what the dog gives you." You say you cannot get this dog to look at a sausage/tug or sleeve in Prey, so that is not something he gives you to train with.
I don't know how stressful your trainers civil agitation is, if it is just eye contact and stalking, or flanking and other more physical methods, but the facts are there are few dogs, even poorly bred dogs that wont respond if they think their bacon is about to go in the fire. You just have to find where he keeps his bacon.
I can hear the howls now "Defense smashes the dog, first build confidence, start in
Prey only!!!!" But this dog is already full of confidence so no need to worry, you just need the right method to trigger his Defense.
I am sure your trainer is well aware of all the old fashioned techniques like flanking, toe twists, etc. but you really don't have to get that physical with most confident dogs. If you go to the K9 PRO SPORTS web page on our forum you will find posts about techniques we call Fence Kicking, and Twilight Raids, these are types of civil agitation that touch a dogs sense of responsibility and will fire up almost any dog. It is a little lengthy so I wont bore everyone here.
Sounds like you have a really nice dog, can't wait to hear how he does after you figure out his combination.
Butch Cappel
www.k9ps.com