The Gap Theory employs Isaiah 45:18, but that verse does not say 'God did not form and establish the Earth as a waste.' It says He did not establish and form it in vain.
The point of the verse is to liken Israel to the Earth, specifically to give the Faithful courage that God did not form and establish her in vain, despite 'all' evidence to the contrary. She was undone in the time of Isaiah, and seemed without hope. This verse is part of a chapter that aims to assure her that, in the final state of things, she shall be brought up gloriously, according to God's promises.
Thus the verse says that, even as surely as God created the entire general cosmos, and the good Earth, He shall bring Israel up in final glory. Even as He had created the Earth to be full of life, and not to be a waste, so, too, He created Israel in order that she know glory, not to see a final defeat.
He is the Creator, and He shall cause her to know only glory as her final state. This is what He says to her in her deepest hours of tribulation. He affirms her, for He is the Creator and Maker of all His good purposes. He did not do a good thing only to have that thing perish. And He did not purpose to have that thing either become or remain waste.
She seems an empty waste to herself in her tribulation. But, as surely as God created and made the heaven and the Earth, she shall not remain so. Her final eternal state, after all tribulations and testings, shall be a state of glory.
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The Gap theory presupposes that God's 'original' creative work was all-in-a-moment, all fully established in no time or process at all. But that would leave us with no model to follow, and no evidence of Divine Wisdom as far as concerns the actual work of forming anything good. The Gap theory presupposes that the general cosmos is created for no practical human use, as if humans, as such, are just God's caged pets who He created to do 'Divinely' amusing tricks of 'obedience'.
Abraham was no 'Obedience' Machine of 'Faith'. It was not obedience that earned him the title, 'Friend of God'. It was faith. Obedience without faith is empty, at best. And God did not command him to sacrifice Isaac. God pleaded him to. The Hebrew word that the English translators translated as 'now' in Genesis 22:1 is, in every other instance in the Hebrew Scriptures, self-evidently to be translated as 'please', and this by one person of another of equal or greater status. So have the English translators translated all those other instances. But in this one instance, the status quo 'faithful Christian' intuition is that, since God is God, God has the right to command A.N.Y.T.H.I.N.G. of us.
But, if we are to accept that God commanded such a thing, then what explains the fact that Hebrews 11:17-19 mentions only Abe's faith? In other words, if we are to openly and uncritically welcome the idea that Abe was duty-bound to 'obey', then, to be consistent with thus idea, we must also welcome the idea that Abe's faith was merely an added and entirely contingent blessing.
But, if we welcome that, then we are, by effect, welcoming the idea that Abe's faith was simply Abe's rationalizing to himself as to why he has assented to 'obey' the (supposed) command. This is because the results of such a rationalization is indistinguishable from the results regardless. Thus, we are, in effect, welcoming the idea that for God alone, might makes right: that 'God is right to command anything of us no matter how abominable, and that He has the right to command it of us for no reason save that He rightly can.' In short, no faith needed; no thought need; no reason needed; Just obedience.
This treats God as incapable of making a plea. Or, at least, it presupposes that God surely did not merely plea here, 'Since, otherwise, Abe would never have complied'. But Abraham was no Everyman, unlike Job.
Job was the epitome of the Everyman, both in Job's righteousness and in Job's suffering unjustly. But Job was a Fallen man, and so Job was a picture of Christ by Failing to be Perfect. For, Job ever only defended his own innocence, never praying for his friends. Not until this one fault was pointed out to Job did Job pray for his friends. Then God brought Job health and wealth again.
As for God supposedly commanding Abe to sacrifice Isaac, this supposition treats God as having HAD, for one or more reasons, to command it. But think of God's relation with Moses. Is not Abraham greater than Moses?
Did not God intend merely to provoke Moses to seek God's honor, when, after some time in dealing with the People of Israel after having miraculously delivered them Egypt, He said to Moses' essentially, 'Hey Moses, this People is getting too much even for Me to deal with. So let's you and Me go and make another People instead of them, and you can be the founding father instead of Abraham.' Moses's did not think to himself, 'This is command, I better assent to it.' No, Moses's reply to God was essentially, 'God forbid: God must uphold God's honor among the nations, lest God's repute be soiled after He had done all the miraculous things that He had done for the People of Israel.'
