"When I first started drinking large amounts I would get light-headed."
I think this is like breathing deeply a whole bunch and you get dizzy. Like you said the brain isn't used to all the oxygen, but gets used to it, and loves it.
Coffee enamas are supposed to be great for detoxing the liver. So make the coffee, then pour it into your ozonated water and get the best of both worlds. Just don't heat your ozonated water, or you'll lose the ozone.