nicotine salts might help as you suggested.
You could also try mixing something at 1.5 mg/ml. Just make sure you give it a good shake and let it sit a while. If it doesn't blend well you can hit pockets of concentrated nicotine when you vape. Especially if the eliquid is cold or has a high VG ratio.
Vertigo can also be related to a problem with the inner ear. I wonder if vapor can reach the inner ear if you are blowing out your nose? I never looked into that idea. Perhaps the nicotine is causing vasoconstriction or inflammation in the inner ear. Although I would think the cigarette smoke would as well...
Are you a dual user? As in, do you smoke and vape? Maybe it has to do with factoring in the overall amount of nicotine you are getting from both sources.
The only other wacky idea I can think of is making sure you are very hydrated before and after vaping. That's very generic advise, but hydration can solve a lot of problems.
I think my only option left is to put very small amounts of nic in the eliquid and work my way up.
I do make sure I shake it for a solid 5 minutes. I've even tried airing it out for an hour or so.
When I first starting vaping, I stopped smoking entirely for a week, so i'm certain it is not duel use. I don't exhale through my nose either.
Yes I also constantly drink plenty of water.
The other issue is the feeling of being stoned it gives me, is the really weird symptom, almost like a dissociative so im not sure if an ear issue would cause this?
My nic salts arrived today so I will update after I've tried this