I agree with posters about the 'touched-out' thing and I see that is something your DW has mentioned too, PseudoDad, and that you have acknowledged as well.
The thing is, while I can quite clearly visualise the physical, mental and emotional feeling that accompanies that ... I can also see what a lonely 'place' that is for your wife to be in.
Can you imagine? Her knowing the gulf is getting bigger. Knowing how hard you are trying; perhaps imagining that it is her own 'fault'; lonely and alone in the problem BUT ... because of the touched-out' thing ... unable to turn to you for support in that 'aloneness'. Unable to say 'I need a cuddle', or to lay her head on your shoulder, or act in any way that could give conflicting messages of 'encouragement'.
I'm not meaning to be dramatic, but do you see what I'm saying?
So ... could you help her? Do you think it would help her if you could say to her
"I know you don't want us to have sex for the time being, and I understand, so agree with that, but I don't want either of us to be without the support of the other because of that. So would it be a good thing, DW, if I promised we won't even try to have sex for (say) at least six months ... but lets talk, anyway ... let's laugh, hold hands, communicate in non sexual ways. Lean on me if you're tired, DW, ask me to rub your feet if they hurt, zip up your dress, wash your back even ... but no matter what we do, though I hope we stay close ... I won't try to initiate sex, nor presume that your action is an initiation of sex, because we've agreed not to have sex in that time ... but let's stay close."
Do you thing that could help both of you stay closer. Let her see that, sex or no sex, you are her safe place and she doesn't have to be alone with any of this, that you'll be right beside her.
Sorry to be so long-winded ... don't even know if how I'm putting this makes sense (anyone?).