to EBN someone will be by to give you some advise. Thank you for rescuing Boris. It could be a reaction from meds or a fear from his past. Any antibiotics should be finished otherwise the his issues might come back. Talk to your vet before stopping. My best suggestion is to take something on your walk to break his focus like a favorite toy or treat practice the watch me command and make him focus on you when a person, bike, ect is near. When he stops his bad behavior or the person, bike has passed give him his treat or toy.
When I walk my dogs I make them sit until the person, bike, dogs ect... has passed. I correct them in the sit position if they start to have any reaction to the passing person/ dog ect..