That is tough. I'm sorry you are going through this.
It sounds to me like you might need to ask the vet about some kind of anti-anxiety medication for Hitch when you leave him alone. Some on the board have used melatonin to help relax their bullies while they are away but I know there are other options. My sister's lab did something similar when left alone and she had to manage it with medication while she worked on getting to the root of the behavior, which takes time.