I don't have a problem sharing stories, but you won't like what I have to say. First off, I think your trainer is way ahead of where he should be. That is not how you bring out the natural aggression in a dog. If he went into avoidance, there was much too much pressure to start in the beginning. I admit I don't know much about PPD, but I do know a lot about training dogs to be aggressive. It would have been two lessons for me, with that trainer. My first and my last.