Hi Woodywasp
You are in the middle of things aren't you. You have said that your wife is in the midst of PND - so her behaviour will be irrational. Have you read up about thsi condition to help you understand what is going on. Have a look
here
It is very important to be patient, as your actions may put your wife off more. It is important for the sake of your son to act wisely and carefully along the way. As I said earlier you can't do much, however much you want clarity and a solution. Dealing with someone who is depressed is very tricky - you have to be the strong one who doesn't get drawn in to her world view and who is steady and reliable to support her when she emerges from it all.
Keep a cool head
Liz