An ENG test is a series of tests usually involving tracking (lights) with the eyes, and then the ear canal is stimulated using either water or air. Electrodes are fastened onto the face to track eye movements. This test is done to see if there is vestibular damage, although it is certainly not complete and perfect. It can make some people very dizzy/nauseous, others aren't affected as badly.
As for the "poisoned" feeling you have,not quite sure what you mean, but some of the things I have felt is, brainfog (unable to focus) anxiety coming out of nowhere, just general malaise (something's wrong but don't know what)
lots of fatigue, etc. etc. Besides the feelings of swaying/movement.
I'm sure with your experience you have seen a neurologist but maybe if you visit an ENT and they do some testing, you may want to try and see a neurotologist to pinpoint what is going on if they recommend. I think it would certainly be worth checking out...
Inner ear stuff can overlap with neurological stuff (i.e. MAV) where the two conditions kind of play off each other. But you may have something going on separately with your ear too...
Hope you feel better and also if you read some of the information archive stuff it can give you a lot more complete info. than many doctors will bother to do!