5 Month Old is Biting/Food Guarding

[Angie1606]

My border collie has shown tendencies toward food/bone guarding since he was a young pup.  He would growl when certain family members got near while he was eating.  We started hand feeding him, which helped a bit but didn't solve the problem.  Just a few days ago, he bit my son when my son tried to pick up a plate he was licking off of.  A few weeks before that, I took him to play with another puppy (same age and size), and he snarled and snapped at that dog when it got near because my dog had found a bone in the yard, and he consistently growls at my husband if he gets near while he's eating.  We have an older border collie mix, 6 years old, but the pup has no problem sharing with him and has never showed any aggression toward him (that I'm aware of), nor has our older dog (who is VERY passive) shown any aggression toward the pup (around food/bone or toy issues).  I should also mention that our pup was attacked and bitten by a much bigger dog when he was about 3 months old.  I think it made him a very nervous and sometimes frightful dog.  He has since been to puppy classes, where he enjoyed playing with those dogs fine, and we will be starting obedience classes next month.  But he is wary of most dogs we pass on our walks and will growl and snarl at larger dogs.  Is there anything we can do to help him learn to be a bit more social/less afraid, especially around the food/bone issues?  Thanks for any help or advice any of you can offer.