You're saying the Hebrew rendered as "in vain" in Isaiah 45:18 is the same word rendered as "void" in Genesis 1:2? And the word implies an actual event? If so, there seems to be a great deal lost in the translation - neither rendering implies a cataclysmic event. It's late, or I'd look into this more, but it really doesn't look like Isaiah is saying anything here other than the fact that God had a purpose in creating the Earth.
Gen 1:28 And God blessed them, and God said unto them, Be fruitful, and multiply, and replenish the earth, and subdue it: and have dominion over the fish of the sea, and over the fowl of the air, and over every living thing that moveth upon the earth.
Just something to think about...
To my knowledge the only translations that render it "replenish" are modern revisions of the KJV. The NKJV, NASB, NIV and 1611 KJV (I believe - I'm not 100% certain on that last one) all render it "fill".
Just realized the quote from Genesis 1:28 wasn't from you. Sorry about that.
No, God created the world and the universe in 6 days
Else, Exodus 20 is a lie
So is Genesis
The "Gap Theory" is not supported by Scripture. The earth did not "become" without form and void, it "was" without form and void.
Sin did not destroy a pre-Adamic world.
Rom 5:12 Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned: