[Nlkko]

^Yes, the collapsed trachea is a result of incorrect use of the leash. To be honest, for people who aren't accustomed to it, a snap and release leash correction is kinda hard to master. I mentioned other methods such as a slight nudge on the side. Works pretty well with mine. The purpose is simply to divert his attention from whatever he's fixating on.

OP: It's best to anticipate the reaction and give slight corrections before it escalates. Anticipate the appearance of another dog/kid and give multiple small corrections because when he's going at it, it's already too late.

Another thing I've found to work wonder in terms of keeping my dog from being distracted is giving him something to do. I give him his most favorite toy (a tiny rubber soccer ball) to carry by his mouth and he seems to focus on carrying the toy instead of stopping, sniffing around or paying attention to other people/dogs.

Edit: Yea, everyone who interact with him have to do the same thing you do or it will be impossible. Try talking them into it. Everyone has to be consistent so he knows that every member in your family ranks above him and he cannot turn to one particular person whenever he's being discipline. I hope he will get in better shape soon. Do let us know the progress!