Hello and welcome. My name is ***** ***** I have been in the dog field for 25 years. I am a Therapy Dog & AKC Evaluator/trainer/ specializing in behavior. It will be my pleasure to help you today.
Unfortunately when we adopt a dog we never know the history of the dog, we only know what the former owner tells the rescue and that is usually not the full truth.
It seems like there may have been a problem with men in the past that the dog is bringing to his new home. Men have a way of approaching people, they are usually tall and walk in a specific manner , with baritone voices, which may be frightening to a dog. Dogs stand in a specific way, or show a specific body posture, when they are frightened and they usually give warning as well, that says do not come near me. Again there is a reason for this and we just may not know what that reason is.
The fact that he rolls on his back when you come into the room is a kind of defeatist attitude, though without more background it would be hard to say why. He may think you are going to bop him on the nose, or pull the choke chain, so he just gives in before that can happen.
Generally older rescue dogs, meaning they are not 8 or 9 week old puppies, need many months to feel secure in the new environment, and need to see the consistency and structure of the home and new owner before they know how to act, or before they know what is expected of them.
Hitting and pulling a choke chain for wrong doings is not recommend, as it has been proved time and time again that aggression gets aggression, and this is especially true with a rescue with no background. It actually sets a tone for them to follow, and the owner does not realize they are setting this tone.
Most of the problems you mention can be corrected by using positive training and redirecting the dog to appropriate things to do. When we say no, or pull on the choke chain, it only interrupts the behavior for that moment, it does not tell the dog what you expect it to do instead, and so therefore it happens over and over again because it is nothing more than a circle. Growl, =no = hit . Growl = no = hit. There is no teaching in-between of how you want the dog to act, so he is always failing. I suspect he has been placed in failing situations by previous owners as well, or he would not have been given up to the rescue.
I am going to suggest that you get rid of the choke chain as they are just dangerous to a dog that size, and I will suggest a martingale collar, snap collar, or a head halter, for training purposes. As well let's try clicker training so that you set him up to succeed and not fail. Train several times a day in short sessions as your schedule allows. By doing this you are showing the dog consistency and structure so he can see how you want your home run. The more positive behavior he is rewarded for, the more you are likely to see it emerge. This tells him what you want from him.
I would say that when out and about while training, if a man approaches you, ask the dog to sit, and ask the man not to make any contact with the dog, because at this time if he does, the dog is going to growl, and since we know this, then we are setting the dog up to fail. .
I would do Behavior Adjustment Training (BAT) when it comes to working up to the dog getting used to men. This will take some time, nothing g happens overnight if the dog is acting out of fear.
Eventually you will have men drop a treat on the ground for the dog and walk away, so the dog sees that good things come from men. Gradually you will work up to them calling the dog’s name , dropping the treat then walking away. Once you see the dog looking forward to see men, you will have them hand him the treat directly, but only when you see the tail wagging up high as a man is approaching
I am going to suggest that you invest in mind stimulating toys as corgi’s are a herding breed, so they need that mental stimulation. Parsons Russell’s are just off the wall in general when it comes to activity level, and some of this activity has to be redirected. Mind stimulating toys are good for this, especially when there is not enough time in a day to train. Amazon has many of these toys for dogs, just type in dog puzzles.
You have a mix of two pretty smart breeds so obedience and trick training should be easy, but it has to be done in a positive method, this gives the dog some confidence in itself and thus should stop the growling.
I am going to direct you to a site to take you through clicker training and to one on BAT to get you started. Between the dog puzzles and the training this should take away the chewing and other unwanted behaviors. I would keep all shoes and bottles out of the dog’s reach for now, as this is an unwanted behavior, and if they are left in his presence, you are setting him up to fail.
If you have any other questions please feel free to come back and ask.
Clicker training/positive method training/ print off
video’s to see how clicker training is done, scroll down to videos http://www.clickertrainusa.com/clicker-training-videos.htm
Training method BAT http://empoweredanimals.com/