ubiquitin, I’m happy that you liked the story!
You’re right, even if the 7 days of creation wouldn’t be literal, we would still have to keep Shabbos every seven days (nice example you gave from sukkah!).
There is definitely no worry of people actually not keeping Shabbos because of this (the story was just for comical relief. Although I could imagine someone coming up with this סברה just to excuse himself, but that doesn’t make a difference).
The point I was trying to make (as I have seen written by gedolim) was that just as we take the 7 days of work literally, there is no reason not to take the 7 days of creation literally, unless we would have a true Torah’dike reason to think so.
The fact that currently there are scientific theories that “prove” otherwise shouldn’t make us learn apologetic interpretations in the simple pshat of the Torah, Midrash, Gemara, Rashi, etc.
(especially according to the Malbim (and many others) which Reb Eliezer brought)
However, your point is true that there are times when Torah tells us that something is a משל, and I wouldn’t say that believing this regarding ששת ימי בראשית is כפירה.
מנחם שמו