I admire your honesty.
Hitting a dog isn't going to teach any dog to trust you. You say from "Day one" why was the dog a problem then? What have you done to solve the issues?
Food usually works to train any dog, coupled with lots of calm talking, petting, and socialising.
A dog wandering around for seconds is a danger to other road users let alone the dog itself, and two hours! This dog could condemn an early death, and even worse you going to court for neglect.
I would go back to basics with this dog before giving up, however the problem may not be with the dog, but it'