Sounds like he is completely bored. Have you thought about taking him to training and your the handler? It's nice that you sent him away, but did you learn how to work with your dog? Obedience classes can do lots for the owner and the dog. It sounds like no one is a strong enough leader and he knows he can do what he wants. Mine is 14 months and she has gone through 4-5 classes, a couple one day classes, and now she is in agility. I still work obedience with her daily. There is a balance of mental and physical exercise with these dogs..some might need a little bit more of one then the other.
Misty- Samoyed Mix
Tannor- Golden Retriever CGC
Robyn- German Shepherd CGC, TC
Midnite-German Shepherd CGC, TC
Brennan- Golden Retriever CGC