Bible supports Atlantis/Flooded world theory.

No, I don't think it supports the Atlantis theory. In Genesis, after Cain killed his brother Abel, God's punishment for Cain was for him to wander restlessly. He lived in the land of Nod (Nod which means wandering), probably figuratively meaning that he wandered restlessly just like God had punished. There is no mention of a group of people already living in the east of Eden, in the land of Nod.

Previously, the Bible says "In the course of time" (Genesis 4:3), we can assume Adam and Eve had many babies 'in the course of time'. So I figure since females were 'insignificant' in the olden days, they fail to mention any female births of Adam and Eve or anyone else with the exception of very important figures. (The same goes with males; the Bible doesn't name every single birth, only those relevant to a story.) Cain just had children with his sister.