Have you ruled out ear wax? That can easily cause vertigo.
Diatamaceous earth will absolutely help with brittle nails. It will also make your skin soft and your hair will grow faster. Start with 1/2 tsp in 8 oz of water. Move slowly up to 1 tsp three times a day in 8 oz of water. It will also help with parasites in the intestinal tract.
Look into MattK3's protocol for info on parasites in the central nervous system. (CNS).

Have you had your inner ear checked? The vestibular system is usually implicated when vertigo is experienced. Could be inflammation or some kind of abscess. Be careful if administrating antiparasitics especially when not under a physician's care with such symptoms. Though I know physicians seem to be less than helpful when it comes to treating parasites. A smart patient will use them for what they are willing to provide alongside their own self treatment. Vitals, bloodwork ie; liver enzymes,CBC, blood cell morphology etc.
Im.sorry you're having such trouble. Vertigo is very scary and uncomfortable to experience.
Have you had a spinal tap?