You've been given some pretty good advice. One thing I probably wouldn't do is keep petting him after he has just growled or snapped at you since this is reinforcing the behavior.
I don't have this problem with Gunther (at least not with humans, he will be possessive around other dogs), but Keiko has gotten worse as she's gotten older, so we've had to work on some reconditioning with her. As with you, she could care less about her food, but her vice is bones since she rarely gets them. I have gotten back to the point where she is not bothered if I go in and move it around or pick it up.
What I did was very simple. I went in, reached slowly for the bone and watched her at the same time. At any sign of aggression, I would grab her by the collar (for a puppy I would scruff), tell her firmly "NO" and pick up the bone. I would then hand it back to her and wait a few more minutes and repeat. If there is any lip curling or growling again, another scruffing and a time out with the bone being put away until the next day. I would then repeat each day until I could take it away no problems. In fact, by the second day she was much better and really sucking up when I put the bone down and needed alot of lovin' before she would go chew on it. (I like to think she knew she had misbehaved the day before and that was why her bone was taken away)
With Gunther, as I said he's not human aggressive/possessive, but he is with other dogs at the park (only with dogs he doesn't know well). He has learned he must walk away if I tell him to leave it. I am even surprised at how well he listens (although it has taken almost a year to get him to this point). Even if there is a group of dogs playing with a toy, or wanting the toy he has, if I tell him to leave it, he will actually walk away from the group of dogs and come over to me. Sometimes I will have to tell him leave it again if he heads over to it a second or third time (if it is a really good toy........lol), but many times he won't go back to it at all for the rest of the time we are at the park.
There are many methods you can use, and I'm sure the website referenced gives several ways to help. You have to find what works for you. I agree that since he is a puppy still, you should be able to curb this fairly quickly, but no more coddling or he will walk all over you.
