I'm not sure that dogs with behavior problems can be blamed on abusive treatment. I know that my dogs have never been abused and I still have behavior problems. One of them I'm pretty sure it is a family trait as her mother does the same thing. I'm referring to barking at sounds and movement. I think they have a tendency towards being anxious and the best thing for them is to do something that helps them create confidence for themselves. I've put my problem child on the treadmill to give her some structured walking time that I can't do outside. I saw changes in her right after the first time. Sadly, it hasn't changed her barking habits yet, but I maintain hope otherwise I would feel totally frustrated and take it out on her little fuzzy self.
Another thing that is a confidence-builder is clear understandings of what you expect of your dog, for both of you. If you start something, follow through, don't give in midway. That makes them unsure of who is boss and they start thinking that they are. That's not good for them or their relationships with people.
One suggestion is the NILIF approach. That stands for nothing in life is free. They have to do something to win your approval. It might be as simple as being petted after you've given them the command for "Come". They don't get to do anything with which you disagree. As I have found no sure-fire way to stop the barking, I'm assuming that it's a long-term process. It was with my other problem barker and she has improved, even if only slightly.
Just don't get hung up on what might-have-been. Deal with what is right now. That's how dogs live their lives - in the moment, so any discipline has to come within a few seconds to be useful, the same for approval.