Thanks everyone for the additional ideas! I had started the thread several months ago, and just recently I've gotten more responses. Just to update, I've been keeping him either on my lap, on a leash, or I close the door. There was one day I got busy with a customer, and a guy walked in the store with Chewy and asked, "Is this your dog?". I freaked out and said, "Yes, where was he?", and he said, "He was trying to make friends with a pit bull."
Needless to say, now I keep a much better eye on him, and I don't trust him with an open door.
