You are not a bad dog mom! You have recognized an issue with your dog and have taken steps to deal with it by discussing the situation with a vet and enrolling in classes.

Is there another pet store near you? I would not ever go there again if it's possible to avoid it. How rude of them. Why sell a product they disapprove of? The employee and the manager should be reported but if that's how they want to run their business then they will lose business.

I think you already know the problem - you need to learn how to be alpha. The obedience classes should help. Maybe you can find some good books? Sorry I do not have specific advice on this issue - my dog is the most pathetically submissive creature. I still had to learn to be a little bit of an alpha to get her to eat - submissive dogs expect someone to be alpha. I got good advice in the dog behavior section - feed her after I eat, do not look at her, leave the food for a set time period. Dogs interpret things very different from humans so your behavior without you knowing it says a lot. An expert can help you send the right message.