He is a cutie! My 4 year old son recently saw a bull terrier at the mall(some event was going on there). The owner let him pet "Bob" and afterward my son said "That dog was funny - he was SMILING!" lol
I'm not a dog trainer so I can't really give advice. I've dealt with dogs growling over possession of something but that is not your dog. Your dog is fearful. Those dogs running up to him are scaring him - the old, calm ones aren't scary. Messing with his feet is scary to him as well as approaching him when he's lying down.
If you fix his insecurity you will fix these reactions.
Sorry I am not more help. You need a decent dog behaviorist - not a trainer.
I'm not a dog trainer so I can't really give advice. I've dealt with dogs growling over possession of something but that is not your dog. Your dog is fearful. Those dogs running up to him are scaring him - the old, calm ones aren't scary. Messing with his feet is scary to him as well as approaching him when he's lying down.
If you fix his insecurity you will fix these reactions.
Sorry I am not more help. You need a decent dog behaviorist - not a trainer.