Well, the OP has not checked back in for awhile? And hopefully all is going well? But Fear or Aggression can lead, to the same thing? If one is not careful. A Dog with a Bite history, that is someone getting hurt.
Pro's say the average pet owner can not, tell Fear from Aggression and they can't read dog's? Many, many years ago, I could not either? But one thing I was clear on, if given the chance my first WL GSD, was gonna hurt someone?
Step one is to realize that "this dog," is not your other Dog's. The owner is the first step to "Rehab," and from there ... you just have to "Figure Out What To Do?" Trying to mold a square peg dog into one's past round peg dog mold shape? Is usually not going to work out to well?
If one insist on shaping a dog that, is just not suitable to "one's expectation's?" It is much better to just "Rehome," them to a more suitable owner, before they have a "Bite History."
If one can't "except," hmm lowered expectation in the beginning, then they should just give the dog up before it hurt's someone? I had one such, not what I expected dog. And I just kept it simple. My dog did not have to like "people?" But he did need to be "Civil Around People!"
And just as an aside alot of LE K9's (WL GSD) have issues with that! A lot of those guy's are not as "Good," as most assume they are. Just saying.
I just, walked him .... a lot! Many, many miles over the long run. And my goal was "Exposure to People," but not Contact with People". And he (became) comfortable with that. So well then we will go with this. Now I modified the "Who Pet's my Puppy or Dog," bit a little. I added a 5 foot stopping distance, if some one looked to interested in him he went and stayed behind me. At first I told him "Stay," but after a bit more time ... I found that was no longer necessary, saying Stay? I stop and he stays behind and waits. While I explain "why JQP, can't touch him." And most people where good with that.
Now his first contact with a stranger (after a couple of months or weeks of this?) I don't know cuz my dog my time ... I didn't care. It was a further down the road neighbor and he would watch us either, step aside and let people or dog's pass or cross the street to avoid ... cuz I got tired of saying, "he is in training" and he was, he was being trained not to bite the crap out of people but most never asked "trained for what?"
Or if I did stop to talk my dog was always behind and would he lay down or Stand. Now this guy had seen us for awhile. And I am just JQP (well probably a bit more but I don't get paid and I only do "Pet's/Rescues.) Now what that means, is I "Can't Proof My Work?" I work alone so I don't have a staff of paid workers to "proof," my work with people?
So we are going around the block and I see someone up ahead? Ok no big deal, we cross the street to avoid an encounter and he crosses back to intercept? Aww crap ... here we go again?
I can't go back across the street because my dog would "Know," something is "different is going on?" And trust me he would. So we meet and I stop feet away (per the norm )and Rocky stays behind me and sits. And this guy is a bit different?
This guy does not ask to pet Rocky (at first) instead he ask ... what are you doing? So I explain uh pretty much what I have said here. And then he stuns me! He looks at me and then "Rocky," and then ask "Well has it worked?" Well no one has ever asked me that before?
I was stunned and answered ... "yes I think so?" Well LOL, not good enough quite yet for him? And he then ask "well can I pet him?" OK ... what is going on here? I look back at Rocky to see what he is doing and "Now," I know what he looks like when he is "fine." And I see the "Same Old Same Old Look," on his face ... ie "Nothing New Here?"
So I step aside and say "OK?" He steps forward pat's Rocky on the head and say's "Nice Dog," you have their. So finally, my job was done (for the most part)! I owe that guy a great deal of thanks.
Rocky went on to become one of the best behaved GSD's at the Vet office for God's sake? He did not need to be Muzzled or Drugged? And he did get to many people around town ... he went everywhere with me. Now that guy and I never did see him again but I own him a big "Thank You!"
Only thing I know is he was EX-Military, and I suspect an ex K9, trainer? He was much to willing to pet a 113 lb Wl GSD, that I thought may or may not have still have "people issues?" But he knew what to look for.
Now I do have another story about a "Fear of People Boxer," that was my first "Boxer," to work with, at Boxer and Buddies. It was an all America Boxer and I was quite surprised (at the time) to hear that there was such a thing (as a fear of people Boxer) but that is another story.
Back more directly on point Fear or Aggression, at the time I did not know but Rocky struck me as ... not "Fearful?" The low growl thing and he locked eyes on company ... like they were raw meat? I was close to him so I felt the rumble in his chest (when company came over for the first time.) And that cold shiver down your spine, yeah that is thing? But he was in Place (which I did not know was a thing at the time) and "Stayed," by my feet and I just kept company away. No you can't pet him ... Struddell was busy greeting everyone and being the center of attention.
But there is nothing under the sun New in dog training someone, somewhere has already done it. What the OP is currently doing, intentional or not ... is "Flooding The Dog."
There are several methods that are still quite popular for forcing a dog to "face its fears." Unfortunately they usually backfire.
Now I would say "Flooding," is/can be a legitimate approach? You just overwhelm the dog with "that which he fears until he just breaks down gives up and "get's over it?" That can work but I much prefer to build a "Bond of Trust."
And how number six can go wrong ... well your "trying to bride, trick "Strangers into your dog's space." And how exactly that can go sideways? Well first if the dog is under stress, they won't take a treat anyway? But if they do ... they maybe so focused on the treat, that they consume it and then look up to see some, A-Hole looming over them and strike out to get away from the threat, WTH??
And you can tell a dog under stress "It's OK," all you want ... "they won't believe you?" "Show Me," works much better I have found, then words when dealing with behavioral issues.