It's not going to help if the behaviour person has the dog walking to heel on the lead and you don't.
YOu need to find a behaviourist who suits YOU. They all come in different guises and have slightly different methods.
Horror dog bolted this morning. He was gone for about 10 mins, then raced back to me so fast I thought he was either going to knock me over or run on. We can't leave him in the garden alone and he cannot yet be trusted off lead.
There are lots of methods people use for making lead walking better. Some people use treats, for the dog to sniff and sniff and sniff before they get to eat it. Some people make it not worthwhile going anywhere while the dog is tugging. I was watching Victoria Stilwell with a bargy dog, and frankly, if the dog is barging you out of the way, who's in charge? I have tried that technique of getting into the dog's space until they retreat and sit and it seems to work. Horror dog is much less likely to crowd the door and race out.
I was recommended getting training IN the house in order. It has helped.
Small alterations to our behaviour can make such a difference to the dog. It's just a matter of understanding what's going on and what changes we can make.
The chewing is normal. Can you use something your pup CAN chew, like a Kong lined with peanut butter? Or a bone?
I'm not sure about the validity of tone of voice. You can shriek at your dog if that's what you do, or you can whisper. If you yell at your dog, it does not mean that you beat him or treat him badly, it just means that that's how you communicate. HOrses for courses.
Dog magazines, like Your Dog have lots of advice from very good people. If you look up the people you will find contacts and professional bodies, and good recommendations.
It's a bugger having an out of control dog. It's hell. I do sympathise.