Wow! That's still pretty high. Mine stopped at 1.010.
I doubt pitching more yeast will help at all. 79F is also a nice temperature and you are stirring.
Have you contacted WineXpert directly about this? They have so much experience with this kit; they should be able to help. They should have a customer support hot line. (I wouldn't bother contacting the shop where you bought it.)
Contact them and please let us all know what they say.
Outside of that, about all I could recommend is to stir everything up from the bottom completely and continue to keep it warm, as you have been. If SG has not changed in 3 days, it is done. If it does not change, I would be sure and add a couple bottles of brandy to fortify somewhat and to make sure the yeast are dead.
I would make that call!!!