Can't you just fuck her in her sleep? Slip some Benadryl into her beverage before bed time. This will ensure she will stay sleeping longer. Try to position the computer with the FB friend into your view from the bed. This is so you can maintain your erection longer.

I don't think your wife is a perv, I think she would have hurt you if you proceeded to ask for head, but then again, I don't know her.