I am not sure what you have, but if it is a dirt floor, then put down plastic, foam insulation, and pour 4" of concrete. Dig down to get it all in if necessary. Consider a hot water piping system to warm the floor. Also my tenderfeet require carpet and pad to avoid the cold feel.
If you insist on wood, use poly and insulate underneath with foam. 3/4" would be a minimum and it will still flex some but the foam under will help. I would opt for the CD grade plywood with eXterior glue like you are using. On a basement floor, I would worry about an interior glue plywood, OSB, or waferboard. Good luck.