Yes, in Genesis 1 the fit to the work week climaxing with the Sabbath does seem unmistakably intentional. And since other texts anthropomorphize God to stress the pattern, such as speaking of God being refreshed on the seventh day, it seems the authors are quite willing to take liberties in order to make the pattern clear. I really appreciated the recent BioLogos article that shows how things like this happen elsewhere in the Pentateuch.
With the compound statements you gave, it’s quite possible to only somewhat agree. For instance, the steep decline after Noah disappears if you plot by time and turns into a bump if you add Noah’s father. Further, your statement implied it’s a steep decline over 5 generations. It’s actually a steep decline between Noah and his son followed by a linear descent (with stairsteps, as I mentioned). After the initial drop to Shem, no other point goes down more than the gap at Peleg in the middle. I agree there’s a big drop, and last post I explained why I think it arose.
That “fact” is a great example of how to mislead with statistics. The 1,111% decline is entirely based on subtracting Peleg’s age from Noah’s and Abraham’s age from Peleg’s. This supposedly helps us understand what is happening in the Genesis 11 genealogy, but that list goes from Shem to Terah and doesn’t even include Terah’s age. In other words, in order to show a trend in this genealogy, this calculation only used one person from the genealogy. The other two happen to be significant people given meaningful, high ages. And, by including Peleg with the first half, the calculation obscures the genealogy’s most significant feature: the big drop right in the middle, underscored by a three-generation plateau on each side.
One could as easily look at the period from Lamech (last person before the flood) to Abraham with Eber right in the middle. Then the decline in the second half is only 8.3% smaller than the decline in the first half. A bit less impressive than 1,111%! That number is meaningless and cherry-picked, and I hope you can see why I hesitate to affirm “facts” like that.
The ages in Genesis show a 350-year drop from Noah to Shem (presumably showing the importance of the flood) and a 225-year drop from Eber to Peleg (presumably showing the importance of the division that took place in his day). Aside from those two points, there is a stairstep decline by hundreds in Genesis 11 and a continuing decline in later ages that moves the numbers into the realm of actual experience the nearer one gets to the time of those hearing/reading the text.
Even as the degree of elevation given to significant people decreases, it still goes beyond what people knew was the actual human lifespan. While I have no problem accepting God miraculously increased a few lifespans, the widespread pattern of inflated, significant ages for significant people leads me to a literary rather than miraculous cause. As @Boscopup noted, even though Moses was given a lifespan of 120, he knew that “the days of our life are seventy years, or perhaps eighty, if we are strong.”