In the end it comes down to quality of life for you and your dog. The end goal is always to have a good relationship with your animal, and enjoy life together. Training is all about being able to live with each other in a calm way, and go through your day effectively communicating with each other.
You have spent a year trying to bribe Jethro into being a good boy. It works most of the time, which shows that you have done a good job showing him exactly how he is supposed to behave when something excites him.
What is happening now is that the bribe is not worth more than the self reward he gets out of being reactive. When a dog gets aggressive, there are chemicals released into the body, including adrenaline, which make the dog feel good. Every time Jethro comes across stimulus, he makes a decision. He weighs the value of reaction to the stimulus against the reward he may receive if he doesn't react.
In training, we often let a dog choose his reward by offering up several different treats and toys and allowing the dog to chose his favorite. This lets us train with the highest value treat to the dog, so the reward for exhibiting good behavior is of the greatest value.
Ask yourself, if Jethro was off leash and left to his own accord, which is how you test for the value of a given reward, would he choose to eat a bit of hot dog, or would he chase a puppy? Which is of higher reward to him?
Keep your answer in the front of your mind.
BAT works because the functional reward, what the dog really wants more than anything, is to be farther away from the stimulus. A fearful dog has learned that he can create space, effectively removing that which is making him uncomfortable, by displaying aggression.
Dog becomes fearful - displays aggression - stimulus goes away. THIS is what the dog wants. A fearful dog won't eat, so that food reward doesn't mean anything. BAT works with a fearful dog because the dog learns that the best way to make the stimulus go away is to remain calm.
Jethro doesn't want the stimulus to go away. He isn't afraid of that puppy, so the functional reward of leaving the stimulus isn't going to work. He doesn't want that puppy to just go away so he can be safe. He wants to be excited and act inappropriately because it is fun for him.
So now you are in a battle of rewards. Every time Jethro comes across a situation where he wants to act up, he is deciding whether the reward in your pocket is of more value than the reward of reacting to the stimulus. Sometimes you win, sometimes you lose. He will never be reliable in this training model because he has too much freedom to make up his own mind, and the rewards are of similar value to him.
You now have a dog that will make up his own mind, which is what you want. Given all possibilities, we would all have our dogs assess a situation and make the right decision, through being shown what that decision should be. You have effectively shown Jethro the course of action you prefer when he comes to a situation he finds stimulating. He has shown that he understands this. He knows what you want him to do. Now he is in a position of making that decision for himself, and sometimes he makes the wrong decision, willingly. That is important to understand. He is willingly making the decision to blow you off and do as he pleases. He is not reacting to stress through fight or flight response.
BAT uses tools to allow dogs to deal with fight or flight. This is not Jethro. He is not acting through conditioned response to fear, he is doing what he pleases because he chooses to do so. It is your responsibility to define what is acceptable behavior, not his.
It is time to stop helping Jethro to deal with his reactivity and show him that he has to listen to you or there are consequences. He will not come to this conclusion on his own, which is what you are waiting for. I know that you want that light bulb moment where he has it all figured out and behaves as you have trained him, just because he wants to. He is just not going to do it on his own. The reward he gets from acting up is too great. It will always be there in the back of his mind.
YOU need to be the boss. You tether him to you so he can't get away and hurt someone. You walk in fear of things that happen out of your control, waiting for someone to walk between parked cars or around a corner, putting you into a situation that , in your mind, you can not control. BAT insists that you manage your dog's
environment constantly, which you can do. Just not wile walking through a crowded neighborhood. That is why you walk at night, when the distractions are so low.
You are not confident that you can handle Jethro in any situation because you have no control. You can get him to comply in a distraction free environment, so you have trained the appropriate behaviors properly. You can add a modicum of distraction and still see compliance to your commands, so he knows without a doubt what you are asking of him. The next phase of training is proofing those behaviors. Jethro needs to learn that there are consequences for not responding in the appropriate manner when given a command.
I know you quit training with a prong because it was increasing his reactivity. IMO, the correction you gave your dog was far lower than it needed to be. Most people nag their dogs to death with too small of corrections. If you correct for the same infraction more than 2 or 3 times, your correction was not hard enough. I understand that this is a difficult thing to do, because you know that it hurts. The last thing you want to do is cause your dog pain. I'm right there with you. That is why I will make it count when I give a correction, especially on a dog that is not fearful. I don't want to pop my dog 1000 times for failing to heel when I turn away from something that she wants to investigate. I do it once, and we move on. You won't hurt your relationship, you will establish it.
Here is what I suggest:
Get your mind right. You have to know, deep down inside, that you have 100% control of your dog when he is on a leash. 100% Get rid of the tether and the belt, you don't need it, and it is giving you a feeling that this piece of fall back equipment is going to save you. YOU need to save you.
Put a correction collar on Jethro, be it a prong or DD, and don't fret over it. Do not be nervous or fearful or worried about your poor little dog. He can take it. Put it out of your mind.
Go for a walk. Don't avoid anything, or watch for things that may amp him up, just walk. when you get to a point where Jethro is interested in something inappropriate, ask him to pay attention to you. Have him sit, down, touch, watch, whatever. It really doesn't matter. Ask him to do something, and when he blows you off, wind up and give him a good correction, harder than before. Don't get mad. Don't feel sorry. Just give him a correction, repeat the command, and then praise him when he complies.
Continue your walk. Put everything out of your mind and just walk. Run through some OB stuff in a distraction free place and mark - treat. Keep it fun. When you get to the next stimulus, repeat the precess. Ask him to walk away, or sit, or watch. If he responds well, praise him up. Mark and treat. If he doesn't respond, your first correction wasn't hard enough. Rinse and repeat. If he comes up the leash after you, string him up. He has to know that you call the shots, period. He can't believe that he will ever win against you, and get his own way.
Your relationship will change from a playmate, to a fun person that Jethro respects and knows he must listen to, and it won't take long. You are at the cusp, you just need that last little push and you two will be happy together. He won't have to make decisions and get stressed out. You be the leader, he will thank you for it.
Disclaimer: there is a very small chance, and I mean very small, that Jethro will try and bite you, because he has gotten away with doing whatever he wants for so long. If you feel this is a possibility, find a different trainer, that is not trying to use the wrong tool to help your dog, and have them help. I recommend going to a SchH club, where they are used to dealing with far more reactive dogs than Jethro. So I say this: if you follow my advice and get bit, it is your responsibility, not mine.