Arolittlebit, (cute name!)

Has your vet ever done sensitivity testing on the Staph? The Staph may have become resistant to the Cephalexin especially if you have been using it a lot. You may have to try a different antibiotic, but do the sensitivity testing first, to see which antibiotic the Staph is sensitive to.
I have Labs too, and my older one sometimes licks her paws. I know that is due to allergies, though.
Good luck, some bacterial infections are hard to get rid of. (Ever thought of it possibly being a fungal infection? Or have you tested for that?)