I'm not clear about BFT's point in dating the document.
IAJ made the claim that the Hebrew Bible marks the first recording that the universe if finite and BFT seems to understand that IAJ bases this claim on the first sentence of Genesis (In the beginning).
As I said before, BFT seems to switch between saying first recording and oldest copy. I haven't run into anything that doubts that the Torah was written or compiled before 250BCE. So I find the Dead Sea Scrolls irrelevant concerning this point.
Per tradition, the Genesis story was written by Moses between
1446 and
1200 BCE. So in a debate on that subject, if he wants to counter tradition, BFT needs to show a document or tradition older that implies the universe is finite.
If he goes with the Documentary Hypothesis, then he needs a document older than about 900 BCE.
IMO, the dating approach is the wrong way to debate the claim of a finite universe. Unfortunately the approach I would take would entail a definition battle. As discussed in the thread,
Not The Planet, the word earth doesn't refer to the planet or universe.
It's just speculation trying to put a date on when the Torah stories actually came to life.