This is a reasonable hypothesis, although I'm not sure whether it relates to "I often wonder if I am closer to reality simply for being poorer
". Since I personally have never considered intelligence to be 'given' - only aquired, like muscles; it is reasonable to assume that swimming in the ocean of thought is a different thing from paddling at the shore. I prefer deep sea diving, so I can imagine the dangers....
Sanity is defined by the average - much like IQ - and anyone outside this invisible boundary is 'crackers' (technical term:). However, there are two ways to be outside the norm; 'eccentric genius' or 'autistic'. Mental illness is not confined to the physiologically stupid (IE, those that have no choice in the matter), but can extend even to the zany professor. You may laugh at the eccentric's inability to tie their shoelaces or remember their doorkey but this is just as serious a mental distraction as damage to broca's area. Faliure to interact normally with the rest of the world can produce a feedback effect, where the less you talk to people, the less you feel able to do so. I call this the 'plastic bag / maths genius theory' - since all serious maths geniuses carry their important papers around in small plastic bags. And wear sandals.
I am emphatically not saying that insane = intelligent or that 'you don't have to be mad to be a rocket scientist, but it helps'. The mind is a curious thing, and cannot be generalised.