Join a good training class so you can learn how to control him and get him used to other people and dogs. You are doing the right thing by making him sit and wait, do this if you have to pass anyone. Take him out for training rather than just when you are going somewhere, so it doesn't matter if you never get to where you wanted to go, and you can turn back as many times as you like. Use a good collar that gives you some control (I use a half check or combi collar). Harnesses are put on sled dogs and horses to allow them to spread the load and pull easier! A dog pulls with its front legs and by the time a harness 'kicks in' the dog has already pulled, and they also damage the dogs back if the owner pulls it back and lifts the dog up by the harness. A Halti can help but does not solve the problem, it just gives you more control.