The dog tried to protect you from your wife. She, probably, has approached you too quickly and inclined towards you - he read it as a threat to you. That fact that she fed him - doesn't mean much, many people think that their dogs should love them only because they are feeding them. Providing food is not the same as feeding treats for being obedient.
Schutzhund semi-trained dogs may bite people if these people remind them the decoy by certain behaviour, and in situations which remind the club sessions. Mainly they bite outdoor, some kids running with the sticks or something similar. In any case, Schutzhund dogs rarely show agression because they they are trained to play and expose positive emotions only. A Shutzhund dog is trained to bite the left arm and nothing else. A different story with a dog trained in Personal Protection. These dogs are trained to protect their owner from the person who can really harm the master, they should also recognise situations in which the harm could be done. They are trained to attack different body parts. And, they are trained tracking, because criminals tend to escape leaving the injured owner on the ground.
I think your dog was a PP trained dog, was meant to be sold as a PP dog, but they sold him to you. The trouble is - very few of PP dogs can make pets, unless they grew up in the family the members of which they were meant to protect.
Nothing wrong with the dog. But you can open a case against those who sold you a semi-trained dog in PP. He definitely was trained to attack in certain situations.