If sex comes up in therapy, stop the conversation and try to redirect it. I get that you want to have a physical interaction with your wife but if you feel like emotional intimacy is as an important component of the experience, then the physical act should not be a vocal point in your sessions. It sucks that its not there, but she needs to understand this fact of how you view the relationship.

That kind of intimacy can't come back after a session.

If you feel so much resentment towards her that you feel like you can't continue the relationship then you need to be honest and tell her. If you want to work towards resolving this and desire her companionship then tell her that. I think both of you need to be honest about your intentions. If she starts throwing up ultimatums and timelines for this to "resolve" itself you may want to seek out your own therapist to help you process the emotions and give you the added strength to make the best decision for yourself, your wife and your children. It is not good to make decisions when you're feeling really emotional.

Open eyes has a really good post to think about too. It's spot on.