A I understand it your position has now become, then, that the Israelites knew rain came from clouds, and that Genesis is therefore an exception to that belief, positing a heavenly ocean with no actual function, but instead just as the content of some mythical belief, or metaphorical function?
The first part is indubitable, for example in the instance of Job 26.8, which says:
> He wraps the waters in his clouds,
> yet the clouds do not burst under their weight.
What, then, do you make of Genesis 9, in which God covenants with Noah not to flood the earth again? The sign of this is the rainbow he sets "in the clouds" (anan, the same word used in Job 26). God goes on to say that whenever he brings such clouds over the earth and the rainbow appears in the clouds (as everybody knew, that happens when the clouds drop rain) he will remember his covenant, and that never again will he send the waters (mayim, as in both Job 26 and Genesis 1) to flood the earth. He closes his speech by, once more, associating the perpetual sign of the rainbow with the clouds.
Now it seems the writer of Genesis 9 agreed with the writer of Job, but was he unfamiliar with chapter 1 of his own book (which even the critical scholars don't believe, attributing both ch1 and ch9 to the same "priestly" source)?
It appears that your continued belief in the "ocean", despite its absence from the rest of ANE literature and even, you suggest, the rest of the Bible, depends on your interpretation that Genesis 1 teaches that the waters are above the heavenly bodies. Can you be quite certain that interpretation is thoroughly watertight (!) against the weight of all that other evidence?
Here's an alternative: On a logical basis (and actually even in keeping with many of those dreadful "ancient cosmology" pictures), the original dark space above the face of the waters in v2, in which the breath/wind of God hovers/broods, becomes in the fullness of time the "heaven of heavens" or "highest heaven" designated as the the dwelling of God elsewhere in Scripture, and somewhat distinct from the "heavens" created on Day 2 to separate the waters.
It is in this original space above the face of the deep that primordial darkness exists, and it is there that the light is created on Day 1, and where day and night therefore start their alternation. Given the fact that the second set of three days is to do with populating the realms created or separated in the first three days, it is perfectly rational to envisage the heavenly bodies of Day 4 occupying and governing the realm in which light and dark, day and night already exist in the scheme - that is the original space above the waters that will, in other texts, be termed "highest heaven". After all, they govern the day and night which first appeared there.
That makes the "inhabitants" of Day 5 neatly divide between the upper and lower waters divided by the firmament - the lower waters produce fish and so on, and the upper waters give rise to the flying creatures of the heavens. The raqia remains the divider between the two (rather than the supporter of the upper, which is never claimed in the text). And of course the animals and man share the realm of the dry land.
If that interpretation were correct, Genesis 1 would mesh neatly with Genesis 9, Job 26, Jeremiah 10, Exodus 24 (and in fact the whole of the OT), as well as with Mesopotamian cosmic geography, the various Egyptian schemes and what little is known of Canaanite cosmology. It would still not be science, but it would be consistent with those other sources, and phenomenologically relevant (by talking of the essential provision of rainclouds rather than a useless body of water mentioned nowhere else).
One would, of course, have to accept that that other unique feature of Genesis - the lattices (‘arubbah) of heaven that are opened to flood the earth (whilst the springs of the deep are also broken open) - might be metaphorical rather than scientific. Given that doors/windows are unique to Genesis as sources of rain, but not as metaphors of heavenly blessing and judgement, I don't find that a difficult step to take, especially in the light of all those rainclouds mentioned at the end of the Flood account!
We can then treat Genesis 1 as a simple, but phenomenologically plausible, account of "the world in which we live", and then concentrate, instead of picking its "science" apart, on why it takes the particular form it does to teach us about God and ourselves.