Hey J:
From what you describe, your dog is already on the edge of getting into a big problem. I would suggest that you stay away from the trap range, and from frozen birds.
I would start off by making sure that the dog was really nuts about birds. Pigeons or quail to start. Then I would start to intro the gun. I would start with a .22 blank or a .410. What you want to do is to fire only when the dog is just about to pick up the bird. Have the person throwing about seventy yards away. Make sure the the mark is slightly down hill, and in short enough grass for you to see the bird and the dog. On your first mark, restrain the dog for a few seconds, and then let him go. Fire with the gun aimed away from the dog, and only when he is just about to pick up the bird. If you start with a .22, make sure that you stay away from the biiger blanks, and start with the crimp loads. Gradually work your way up to a light shotgun load, and then to 20 blank loads. If at anytime the dog hesitates when picking up the bird, go back to the previos step. If you have trouble at the first step, put a gunner about fourty yards behind you, so the dog and gun are about 100 yards apart, and work the gunner closer to you. Once you work up toward a 12g. blank, then you can start to fire sooner, or while the dog is closer to you and farther away from the bird. Banty hens work great for this, they are tough, as long as you keep them dry. By this time, the dog will start to positively associate the gun and the bird. Gradually work up to firing before the bird is thrown.
Always point the gun barrel away from the dog.
When you take the pup on its first duck hunt, bring ONE GUNNER, and have him shoot the first duck the dog sees period. Only shoot at birds that the dog can see. Then you should be in the clear.