I think you need to tell him that enough is enough and that he needs to set up an appointment w/the counselor to see h how best to communicate w/his son. After all, he missed the appointment the last time.
You truly are a saint...because I would have been tempted to ash where he got his PhD in child rearing...that surely would have shut him up and then hung up on him.
It's like he goes through cycles w/this child rearing stuff. He resents the connection that you and your son have, hence, he has to make a big issue over nothing because he wants son to feel the way he does, i.e., as a child.
Tell him that he needs to speak to the counselor on child rearing issues and learn how to communicate w/his son.
Now, off you go and enjoy your evening. Sometimes, have to call on them on their BS and to me, this is one of those times.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.