Isa 45:18 is in effect saying that God did not create the Earth in the way it is described in Gen 1:2. In fact the phrase without form and void is used in
Jer 4:23 I beheld the earth, and, lo, it was without form, and void; and the heavens, and they had no light.
where it is used to describe the Earth after God destroyed it.
I think that your interpretation of Isaiah 45:18 is superfluous at best and eisegetical at worst. The context of Isaiah 45:18 is a "challenge" between God and the false gods, where God proves His superiority by predicting the rise and divine use of Cyrus. Firstly, Isaiah 45:18 does reflect Genesis 1, I agree. But not for the sake of proving the v1-v2 gap - it invokes Genesis 1 because Genesis 1 is really God's trump card: "Those false gods represent created things, but I am the
Creator!"
Secondly, there is a comparison of opposites in vv. 18 and 19. In v18, the chaos which God overcame is compared with the order which God instituted; in v19, the mysterious oracles of dark pagan lands are contrasted with the plain truth of God to Jacob. Clearly there is a parallelism between chaos and pagan idolatry, and between order and God's relationship with His chosen people, so that the "chaos" and "order" are really symbols of the fundamental fact that Yahweh the warrior stands with His people against Chaos and defeats it.
Thirdly, even taking it at absolute bald face value, there is no collision between this and a conventional reading of Genesis 1. Genesis 1 ends with verse 31 where God says that everything is "very good"; by that time God has indeed "formed the earth to be inhabited". Isaiah 45:18 fits perfectly into Genesis 1:31 and there is no rationale to try and squeeze it into the gap
between Genesis 1:1 and 1:2.
As for Jeremiah 4:23, it is clear from the context that Jeremiah is prophesying the destruction of the land of
Judea, and that expanding his view to "the world" is a prophetic use of superlatively vivid imagery. Even if one takes the expressions super-literally and says that the whole earth has been destroyed in this vision, just because this chaos was a result of God's destruction the second time does not prove that chaos was a result of God's destruction the
first time. It is a circumstancial (I'll grant) but not sufficient proof.
[Yet I will admit that your reservations make sense. Why would God create the world in chaos and formlessness, instead of putting order in right from the start? Was Genesis 1:2 a prototype gone wrong? ... this is precisely where the TE position is strong: there is chaos and formlessness in God's creation in Genesis 1:2 because Genesis is an expression of the archetypal order-vs-chaos Eastern creation story, and the villain exists and is vanquished - without ever having to worry about the philosophical difficulty of where the villain came from in the first place, since it's a story.]