Thank you for the additional information, it sounds like you son has been though a lot these last few weeks and this move was the icing on the cake. I understand that divorce is hard on you both.........but it is nothing compared to what your son is now going though. And all the bickering back and forth as well as dads actions is enough to cause a grown adult to become stressed, as for your son its enough to cause traumatic mental harm.
Now please understand I am not trying to lecture either one of you, but the reality is there have been so huge mistakes made here and at this point your son must come first. You both are going to have to sit down and deal with this without involving him in your disagreements...........at the end of the day nothing matters except what is best for your son. What you want and what dad wants means nothing, if it comes at the harm of your sons mental and physical well being.
From what I have gathered your son feels he has been unfairly treated by this whole situation. He has lost his family (And yes a divorce can make a child feel like he lost his family) he is feeling threatened and now is being told he is going to be uprooted from everything he knows and loves. The reality is your son is old enough to have some say so about his life.........and both you and dad are simply telling him the way it is going to be. Now I am not saying that he should have all decision rights, but he should have the right to express his view point and have his desires taken into account. I am sure you both want your son, but if you both don't stop pulling your both going to lose out when he ends up resenting you both.
What I would suggest at this point is that you go to his door and apologize first. Let him know that you both were wrong and how sorry you are for putting him in this position in the first place. Let him know that the situation ends here......that you both are going to make a big change in the way you handle the divorce and that you want him to communicate with you about what he wants. While this may still mean a move may have to take place, the reality is that you are going to try.
After that ask him if he would please be adult enough to come out and handle this situation with you. Let him know that you want his opinion on all this and need his help to make it right.
Now if he comes out great, sit down and talk to him about this. But try to keep calm and explain your reasons while allowing him to express what he wants. Try not to take offense if what he wants does not coincide with what you want.......the reality is he has a right to express how he feels. Today is the day to right the wrongs that you both have done.
If he refuses to come out, you need to accept that. Forcing communication on him is not going to help matters. As long as he is in no danger and he isn't being destructive allow him his space. Tell him though the door that you will allow him time to think about it and set up another date to talk about it. Now I know you want him out of the room.......but if you try and force him out he is going to be even more hostile and resent you even more. He is hurt, and angry and mad at both of you..........but if you force him to talk when he isn't ready he is going to say things he does not mean and end up feeling worse when he calms down. The key is allowing him to calm down. The fact is even as adults we all sometimes become so frustrated and hurt that we need space, your son is no different. Right now he feels he needs to cool down, and the best thing you can do is allow him to do so.
Once this disaster is averted you will want to set him up with a therapist. He needs someone he can confine in and talk to about how this is effecting him.