Nick, what breed is your dog? He is just beautiful!!!! While looking like a "tough guy," there's a certain quality of vulnerability to him. Sure appreciate seeing pics of him.
Buddy is our foster Boxer. We take in the trouble guys and gals "Only dog and often worse behaviors". I wish I could stop the window barking but I think this is mostly due to not getting out to burn off his energy. I have a neck and back injury that is impeding my dog handling at the moment. Buddy looks frighting when he does his barking bit but if you look at the tail it is all wags. He does show that he is terrified himself when meeting strangers , a dangerous thing with such a powerful breed. I have threaded the needle with him and feel I can give him psychical reinforcement when he is getting out of hand "nudges only!", hip bump ect. we never hit out pups or use negative reinforcement. I do believe this guy at least partially suffers from psychical abuse but coming from a shelter I do not know the full story on him. Buddy will need patient dog savvy adopters that are willing to work with him cautiously. I love the guy and will be sad the day he departs for his permanent home.
Nick, I can only congratulate you for what you all are doing with Buddy. Hip bumps are Good!! And window barking I'm told is often a sign of "I gotta get out of here and RUN RUN RUN." Even so, however, you'll make up for it when you get back from your injury, and his ability to detect the pain you yourself are feeling has always to be factored in to the matrix,
He's a beautiful guy and you loving him and being his leader will turn him around. The tail wags are a dead give-away that he's unsure of how to proceed: stay away, but please come close. And you are absolutely right about "patient dog savvy adopters." Your assessment of his early history I'd reckon is close to spot on. Calm, assertive energy wins the day. Keep up the good work.