<>
He may not find a kong with PB all that important. I am sure there is something out there, that he would find rewarding enough to go into the kitchen when he KNOWS he is going in for the day. Try a raw marrow bone...like a knuckle or femur that you can get from a butcher. Try not feeding him at all, until he goes into the kitchen in the morning...if he wants to eat, he has to go into the kitchen.
Other than that, it sounds like you are handling it very well. He may have to wear a lead to get him into the kitchen, then you can remove it. I imagine he was allowed to pretty much do whatever he wanted in his last home...so he is confused with the new restrictions, and boundaries you have put in place (ones that he should have had from the beginning). It is hard when a dog has to start from square one, especially when they have learned that using their mouth can get them what they want. Good for you for hanging in there. He will eventually learn that he has to cooperate. I would definitely use his food for reward for good behavior. Doesn't mean you have to withhold his food if he doesn't cooperate...but you can use his food to help him realize what you want him to do.
