What else should I be doing?
Your location is a big deterrent. It sounds like a local neighborhood. Strangers will be noticed. If someone doesn't "fit" the area, they'll be remembered.
Be alert. Make eye contact with everyone as soon as they enter the store. That tells them, "I see you." Greet them, ask if you can help. Be a "presence". The dog is good. Many people are afraid of large dogs, especially if they bark.
Put an "alarm" sign in the window and a red button in a prominent place. Makes the crook think the place is wired with a panic button.
When I worked "loss prevention" for a large retail chain, we found the greatest deterrent to shoplifting was sales people all around and noticing the customers. Today, I could walk into Wal-Mart and steal them blind. There is no one on the floor. You have to send up smoke signals to get a clerk. Yea, lots of cameras, but they can't monitor them all and they can't see everywhere.
As a last resort, carry a piece, either in plain sight on your person (best place) or just under the cash drawer. Make no secret of it. Crook walks in, sees that you're packing, and walks right back out.
And speaking of that, beware of someone who comes in, looks around the store, and leaves, then comes back a little later (maybe once or twice) without buying anything. A shoplifter I caught at the hobby shop had been in twice that same day, lazily roaming and noticing EVERYTHING. Yea, I know a lot of legitimate customers do that, too, but being alert will scare off the one bad apple. There will be something about the way they act that will make your neck hairs stand up. Most of the people we caught at the retail chain were recognized as having been in several times recently.
Install a couple of dummy cameras. Crooks don't like to be on video.
I hope some of this helps.