As she is refusing marriage counseling, there's no other alternative except divorce.

This isn't going to change because she doesn't want it to. My guess is that if she decided your son needs a little brother/sister, then she'd turn on the charm again. This isn't what you signed up for when you married her; to have a sexless marriage before you were 30yo!

You and your wife are modeling behavior for your son: being an adult, a spouse, a parent. As he grows and sees this, he will have a very warped idea of personal/sexual relationships. PLEASE get out and find someone new. Having 2 parents in two different happy homes is much better for him than watching the dismissive, disgusted repulsion that your wife is showing. You and your son deserve better. Your wife does, too, but only she can be the architect of her better life!