Omg I am appalled at the vets reaction! Holy wow! I have no words for that! I hope his tests r ok. Cutty started being aggressive after 1 year. I had no help like there is here. People told me about the nilf program but reading it all is overwhelming and we tried to have authority but in reality didn't at all. Thankfully neutering him did fix him 99%. Brought him home and maybe he realized we were in control of his manhood so we r in control.
miila came and began being possessive aggressive as she tried to make her place in our pack. We submitted and I don't know if it had impact or if it mixed with everything did but she is 100% better now. Hand feeding I think had the most and quickest impact in her behavior. You have another pup so I would have Ernie sit/stay while the other pup eats, then when it is his turn have him remain in his position while you feed him 1 handful at a time. Before each handful you make him work, sit pretty, hi five, roll over etc. feed slowly on YOUR pace. He will realize you r the pack leader because he has no choice. I am far from an expert but this really did work miracles in our home although it took months for the complete transformation. I know all pups r diff but it can only help to try.