I think this is the most disturbing dog thread that I've ever read.
1. I have no doubt that you're part of the problem. Now that you admit to being afraid of certain dogs you are emitting something they can smell or sense and that's contributing to the issue. I'm not blameing you - I'm just saying that another rider might not have a problem with these same dogs. That might complicate the situation. The problem is - you can't control your feelings so that isn't going to change.
2. If I were king of the world I wouldn't blame you for taking the deadly force road but I'm not and my opinion doesn't matter. I suspect there's both a criminal issue and a civil issue involved here. Even if you win the defense may turn out to be both messy and expensive and have some unforseen and unintended consequences. I think you'd be well advised to consult a lawyer before starting to carry a gun with you. Your sheriff has his own point of view and agenda and doesn't count.