Lots of us wear out our welcomes, Clue. Why be an exception?

I'd start by realizing that I am not going to be able "to knock down" anything at all. This is, maybe, a position you have never been in before -- your child being in-charge of the relationship between you. That can be a very huge difference and one it takes some effort to become used to.
You could start practicing the pronouns and name, I assume he doesn't go by 'Amy' anymore, when you write here.
If you talk with your wife I would be willing to guess that this did NOT "come outta nowhere." Try to think back: there are almost bound to have been some signs. The fact that you blew them off or didn't "put much stock in them" may be one of the reasons he sees you as "not being supportive."
Have you tired to call him, or do you expect him to call you. After all, if you're anxious to talk and he holds the cards, then you better cowboy-up and go to him, one way or another. As a parent it's a bad-feeling position. I know.
I don't know how or if you "made him miserable," but he certainly seems to feel like he is not gonna get a reasonable "hearing." I hate being blunt, but, maybe that's the key: YOu need to take the cotton outta your ears and put it in your mouth. Let him talk and you and your wife finally start to listen. You are not required to "know it all" and since you are admittedly 'clueless' in this regard you should find it easy just to listen.
If you have pleas and ideas about 'what he should do' I would suggest you bury those. If he's moving in 10 days, he obviously doesn't think he needs any suggestions from either you or his mom. But, you might at least make a humble plea for him talking to you two. And LET him do just that if he's willing. He talks, you two listen. (Try to get all your tears and anger out beforehand so you're not tempted to interrupt him.)
I wish all four of you the absolute and very best to come from all of this turmoil. It will be maybe the hardest thing you have ever done if your are successful. Of course, if you are you will have a son you can start to appreciate. Perhaps that's all he's ever truly wanted any way: appeciation.
Nichole