However, I also think there would be no shame in saying this isn't the dog you thought he was going to be, and returning him to the rescue
Where as I agree returning the dog to a rescue who will take him is the right thing ro do, I do believe there is a shame in it.
No one should be taking a rescue dog, sight unseen, who doesn’t have the experience to deal with the dog. A week is not enough. Most people know this is months and months of work.
I took a rescue, my second last dog, who was abused. You need to put in the time and effort, not turn your back when rhey mouth nor walk them up to three hours a day immediately, you need to dedicate the time, the effort, and accept it could be many months before you see the dog relax, particularly an older dog like this.
This dog deserves a home, and as much love as any other animal, and the simple fact they had to be rescued tells you they have been abused or neglected, and you will need ro do a lot of work.
You don’t do that in a week, you don’t do that by turning your back when they mouth, you don’t do that by extensively walking them as soon as they arrive. You do it by giving the dog space. Time. Love ..,,when they are not too scared to accept it. You build up by slow, short, walks. Letting them know you’re there when it’s done. Giving them their space again.
Mine was the most loyal dog I ever had. I simply had to whisper his name and he stopped immediately and looked at me for my command,,he fell asleep every evening with his head in my lap even though He was huge, you wouldn’t want to have looked at me the wrong way when he was around, he was, quite simply, my child. I saved him and he knew it. I would have stood bodily in front of him, and he me. But it took time.
So yes, there is a shame in taking a dog where you neither have the knowledge, willing, understanding or experience to know what you’re dealing with.