Hello and thank you for using this site to help you./ My name is ***** ***** I have been in the dog field for over 25 years. I am a service dog trainer and evaluator of Therapy dogs, specializing in behavior. I am reviewing your question now.
It does sound like you are dealing with a pup that has possession aggression over items he deems important enough to protect. This can get worse as the dog ages and reaches maturity. Dogs with this can eventually deem items, space, and people as a possession.
At this point, I would be picking up all items and making sure the dog has no access to them. You can also limit his movement in the home so that he does not have access to items.
Then I would get a consistent training regiment going using a positive method of training such as clicker training. I would make sure he learn the cue Leave it and drop it to 100% accuracy.
Training should be done daily so you show yourself as a consistent leader in the home.
I would also put him on the learn to earn program, so nothing he gets is free. He must work for you for everything he wants, even petting. You will decide when it is time to play, walk, and I would use his daily dose of kibble as his reward when you train. The holder of the food is further seen as a leader.
Make sure he does not have access to furniture as this also puts them on a higher level and eventually they will begin to claim space.
I am going to direct you to links for clicker training and for the learn to earn.
I believe that once you begin training daily and putting the learn to earn in place his behavior will change. Everyone in the home must implement the learn to earn or you will set him up for failure and it won’t likely work out well.
Clicker training/positive method training/ print off
video’s to see how clicker training is done,(go to videos )
Clicker leave it
Dr sophia yin learn to earn https://drsophiayin.com/blog/entry/the-learn-to-earn-program/