Hi, kofh2u. I'm not here to bash the Bible or anything else.
But it seems to me that your argument's burden here is huge. The number 7 is a mystical number not only in Christianity but in other religions and mystical traditions, from Pythagorean numerology to New Age 7-note chords of creation. The Bible itself is replete with 7s, as well as other numbers of sacred significance.
So your burden here, as I see it, is to provide an argument for ancient mystical knowledge of seven ages of creation that is so compelling that it eliminates the possibility of mere coincidence.
At present, coincidence seems more persuasive. Nor does it seem all that remarkable a coincidence, given how richly endowed Jewish and Christian texts are with sacred and mystical numerology.
My older brother has been married 3 times; all of his wives were born on the same month and day (10/3). That's a remarkable coincidence, but it doesn't make me believe in astrology.
Why should I believe the ancient authors of Genesis intuited the stages of the Big Bang, a staggering notion, for sure, rather than the more prosaic notion that they simply chose a number with mystical significance to enumerate the days of their creation story?
"If you can keep your head while those around you are losing theirs, you can collect a lot of heads."