Never, ever lie to your son again! If your wife wants the divorce he's big enough to take the news. Help him to cope instead. It's her choice, the blame is all hers and she's going to have to own up to it. Tell him the complete truth, edit for someone of his age, and let him make his own adult choices.
Tell the wife that it's time she told her son the truth as well. He doesn't want this crap and you don't need to take the blame for it. You own 100% of your 50% of the relationship. She's the one that's making the choice. Let her face the anger, the disappointment, the fear, the chaos she is creating. It won't change her mind but you don't need to be the one to take the brunt when you are doing all you can. Make it clear when you both sit down with him who's choice it is. This is not a JOINT decision. She owns it and she gets to face it. It's her job to handle her relationship with her son. If her choices cause a rift, well, she's paying the price for her choice then, isn't she.
Again, don't lie to kids. They know. He knows. You lied to him and now you need to repair that as soon as possible before it festers.
