CJ,
Some times, I feel like I write a lot about myself when answering questions. This is because, that is all I have to offer. Just my experiences. I have no formal knowledge or training . I train by intuition and what I read and learn. As you can imagine , it is an iterative process of learning with many course corrections along the way.
Now that I have gotten the disclaimer out of the way, I will honestly tell you what worked for me. You are the best judge of what will work for you and Vince.
So here it is.
Before jumping into the corrections based solution, try desensitizing him sub threshold.Bring him to threshold and then correct.
Step 1: Keep Vince hungry
Step 2: Take him out to a quiet park or a meadow and ask some willing stranger to appear in sight say 50 meters away or 100 meters away. Which ever you think is sub threshold. AND ASK HIM TO STARE AT VINCE.
Step 3: The moment Vince looks at him , click , reward with food.. Repeat this for a few days. PS: I would not be giving Vince the ball once he tenses up, to diffuse the situation. It teaches him that tensing up is rewarding.
Step 4: Then ask the strange man to take one step towards vince. Click / reward. Keep moving the man , one step by one step closer to Vince and some where he will not respond to the click by taking the food, or like my boy Kaiser, will take the food but spit it out. This is the threshold. This is where you need to work.
On a different day (not on the same day if it does not feel OK)
Step 5: Do a very abbreviated version of Step 1 through 4 to re calibrate your threshold point.
Step 6: Ask the man to take one step closer than when Vince spit the food out. And I assume Vince will be glued to this guy because the strange man has crossed that "invisible line" and in Vince's mind it will be like "I can't take this anymore" , BUT HE IS NOT ACTING OUT . Ask him for a totally incompatible behaviour. Like a total down with his chin on the floor (you need to teach him that and proof that before this).
Step 7: If he blows you off, then correct him strongly and tell him that you won't put up with his insolence. The correction should make him go "Wow!! I don't want to deal with my master today".
When he blows you off , you are correcting him for not downing. But the correction it is not for fixating on the man. It is because you commanded him to down and he did not. He blew you off and that is unacceptable.
If you already do not know his "Ouch!!" point. You have to be prepared to keep escalating the levels of corrections disproportionately till he complies. If you are going to increase the correction level in small increments, there is risk of him learning to work through them.
making him go "Ouch!!! that hurt" will teach him that he has to pay attention to you even if the heavens are falling down. It is my intuition that it is not the physical pain that made him pay attention, but the fact that his mom is the one administering it that makes his world shatter to pieces.
I am guessing this because I know how my dogs behave.
When he is all crazy and lunging and you correct, the correction does not quite reach his head. The correction should come before he acts out his emotions.
This is how I taught my dogs Bommi and kaiser. I can make a video of how they behave around aggravating stimulus when I am around and when I am not around.
If you saw me walking them you would think that they are sweetest of dogs. You will not say the same if you saw my helper walking them with me not present in the environment.
As hard as it is for me to say this (because of my human condition, how ever my dogs do not begrudge me for this), there is nothing more in this world my dogs fear than me. If I wanted to sugar coat it, I can use the word Respect.
I am being very honest when I say that I administer HARSH corrections to my dogs may be twice or at the most thrice in their lives so far (1.5 - 2 yrs). That is it!!! God's honest truth!!! I am not making them cry on a daily basis, because I look upon them and treat them as a part of me.I say this with a bit of trepidation as harsh corrections are looked upon as abuse by many.
These are the kinds of corrections that will make my eyes well up with tears when I go to bed because after all they are my babies. But when the situation demands, I will not tolerate insolence. Under no circumstance. There is no doubt in my mind when I take that dog by my left leg that I will do WHAT EVER NECESSARY to achieve compliance. It is very clear in my mind and it is very clear in my dog's mind that I am capable of enforcing compliance.
(PS: When I ask my dog to sit and he stands or lies down or heels that warrants zero correction. It just means that I have been a bad teacher. When I ask my dog to sit and he blows me off and is fixating on the other dog/human then that is a breach of conduct)
If you keep at it, eventually obedience becomes a habit for the dog.
Example: If you look at a soldier saluting his drill sergeant, it is a great example. If you walk up to him and ask him why he saluted , he would say "I don't know!! That's just the way it is"
It is neither the fear of punishment (even though that was the primary motivation in the begining) nor the reward of scoring brownie points with his superior that made him salute. He saluted because he has been conditioned to do so, by 1000s of repetitions. It is just second nature.
This is the sort of relationship that best describes obedience for real world. The dog should not heed your words because it fears you or because it thinks it can get some treats from you. It listens because "that is how it is".
There are some dog's that will break under pressure and those dogs cannot be trained. They can be taught tricks that they can perform under controlled environment.
You cannot have a dog that is obedient 95% of the time. It is like having a balloon that is un punctured 95%.
Either I have an obedient dog or I don't. Sit, down, stand, heel, fetch, bite , track are all little tricks that can be taught with or with out obedience.
Obedience, in my view is just one behaviour trained and proofed.
"Pay attention to my master".
All other behaviours are irrelevant.
You have to figure out for yourself how to achieve that. No one can tell you. Do what your heart tells you. At the end of the day, it is more important for you to accept your dog than for the world to accept your dog. But, you knew that already.
I have a boy kari, whom I cannot train. He cannot handle pressure. I will destroy him if I tried. So I just love him for who he is. The other three can handle it, so I have put them under the anvil and forged good specimens to the best of my abilities.