1) Don't pitch the wheat yeast, that will give you some characteristics you are not looking for in a coffee stout
2) Have you tried gently agitating the vessel to get fermentation going again. I think that would be your best bet to get it going again, especially since the gravity is still so high.
3) If your fermentation started and pumped it down .040 points, I wouldn't worry about having stressed your yeast. Its set and ready to go, a little agitation should get it back in suspension and reactivate it