The article link I posted was sent to me by someone on this forum. It was timely & much appreciated!!
Just read your post (very late). Sorry to hear of the awful attacks, I've had many like this too. About the sodium intake: for me a low sodium diet has definitely helped. If I eat over 1g of salt a day I have an increase in vertigo attacks and like you, spend most of my time crawling to the toilet or lying in bed and vomiting into a large bucket. Have you tried Proclorperazine for the vertigo attacks? It has really helped. Take 3 or 4 5mg as soon as you get the vertigo, go and lie down somewhere (in the dark) and wait for about 45 mins for the drugs to kick in. This is the only thing I've found that helps during an attack. For prevention, definitely try out (give it about a month) a low salt diet. It's a pain but for me, it does seem to decrease the frequency of attacks. Also try Betahistine and if Meniere's disease is diagnosed, ask your ENT for a steroid injection.
I would suggest going to a good upper cervical specialist and getting an adjustment; x-rays can also tell if your Atlas and C-1 are misaligned.