[MyPemCharlie]

What you just described is resource guarding. Jane's suggestion to feed him by hand is a good idea, so that he knows where his food is coming from. Also teach him "Trade". Get a toy and a treat, (or two toys). Give him the toy, but hang on to one end. Then wave the treat (or better toy) in front of him and say "Trade". (The treat or other toy needs to be more tempting than the original toy.) He should let go. You give him the treat (or better toy) and say "Good Trade!" You usually want to do at least 3 repetitions of any training so they start to put the word and action into memory. "Trade" is a good foundation for "Drop It" later on when you may be at a bit of a distance and don't have something immediately available to trade.

Also put his toys away and give them to him when you want him to play and take them away when you're finished playing. This will also reinforce to him that you own everything and share with him when you choose.

The NILIF (nothing in life is free) is also a good idea for a resource guarder. "NILIF" will pull up some good articles on an internet search. It includes several techniques, which when used together, will help your pup see you as the leader.