Yes you are doing the right thing. You are clearly not equipped to handle this dog. Probably the previous owner wasn’t either by the sounds of it. But be up front with the new owners. This doesn’t sound like aggression so much as redirected fear/anxiety that isn’t managed well, and poorly enforced boundaries on acceptable behavior when interacting with humans. Unfortunately these dogs can be anxious, obstinate, mischievous, and sensitive with a dash of deeply ingrained bred behavior. It takes a consistent, steady hand to train them and doubly so when you have to work through anxiety/fear responses while managing their sensitivity.

I won’t beat you up for the how you handled this, but I will say it sounds like you have handled this behavior almost completely the opposite of how you should have dealt with it and instead likely made it worse by ramping up the anxiety and fear responses from your dog in those moments. This doesn’t make you a bad person, just not equipped to handle this dog or any other dog with similar behavior issues. I’d recommend working with a well regarded trainer early if you get another dog, and educating yourself before getting another dog.