Dog's fear and confidence

I'd condition to the muzzle-it keeps people away a bit easier to be honest, exploiting the muzzle stigma helps. Makes that side of things a tad easier, less grabby hands in general.

Make sure you bring extra special treats out and pass them to him whenever he looks at someone or you encounter someone. He doesn't need to be doing anything other than not lunging/barking-reward until the person passes and is gone. If that's too hard, back up until he'll take the treats and give him lots at that distance. You'll know what distance is okay to work at based off his reaction to eating/the stimulus. This is way easier to do out in the bush than in a city, so I would push walks to somewhere less busy/populated if you can drive there first. You can also adjust when you do walks to suit the neighborhood-go when people are busy and are not outside. Koda used to be scared of the dark but she loves night time walks now because it means no construction and fewer dogs around (her weaknesses) so overall less stress.

I have also literally shrieked and run away from strangers who wouldn't listen and continued approaching. "He's contagious" works better than "he bites" because everyone thinks that they know best and they're so sweet why would ANY dog bite them? When it has nothing to do with them and has everything to do with the dog's genetics and environment. When people in the elevator tell me they aren't scared of my dogs, I tell them that's great-but my dog is scared of them, so to please not touch or look at them. Ideally, we get out before someone rushes us into a corner. Do your absolute best to not back him into a situation where he can't run away-and that means preparing well in advance, as I'm sure you've started to experience.

There's lots more that can be said but I think this and the stickies on reactivity would be a good start for you. There's no reason to feel bad, you're working on increasing the quality of life for a fearful dog, and its not easy. People are rude. Good luck!

Ugh, people can be so inconsiderate. I'm not sure your situation - is Cooper a rescue dog? When we adopted Finlay she was terrified of people, especially men. She was constantly out for with me walks and on transit and exposed to a lot of people from afar (so not a contained house dog), and when people would approach too close I'd just say "she's a rescue and quite nervous with people still".

Most people would respect this and stay several feet back - this was good as it let her check them out a bit, and see that they were safe. But so many would say "oh, she'll get over it" etc and lunge at her, which would leave her cowering behind me. One guy watched her and approached (as she was pooping!) and when she scooted away and hid behind me he said "what's wrong with her? Is she brain damaged? She's not normal." I swallowed some rage on that day.

We hired a trainer when her fear of my husband became too much, and the three sessions over a month helped a lot. At the same time I'd started giving her Brewer's Yeast, I'd read a lot about anxious dogs and how their B levels became depleted in stressful situations, and it made it harder for them to cope. I'm sure that the Yeast helped a tonne - she was less terrified and learned to be a bit more confident. I'd strongly recommend it - just be sure to get the dog version (not pricey either, I got 250 tablets for $5, and she loves her daily vitamin).

The thing that really made her the confident dog she is now, was getting our second dog, surprisingly. He was in bad condition and very weak, but quite social and is very friendly with dogs and people. Finlay learned from this, plus she seemed to want to show off and the first night we had him she strutted on our walk while I carried him. She also decided from that moment on that she 'owned' my husband, and physically snuggles into him all the time now. Dogs are weird!

One other thing to consider, is how you react to others. You are probably quite protective (which is good!), but as people lean in, Cooper can likely feel your hesitancy. Developing a stronger reply to people can help you feel more confident when they approach, and Cooper will probably feel that.

I feel for you in this situation, hopefully something works soon.