All good questions.
Remember that God knew that we humans would sin before He created the world and He even planned on a means by which to save us from sin before He created the world (Ephesians 1:4, 2:10). Therefore, He obviously never intended THIS earth to be an everlasting paradise.
Romans 5:12 tells us that death first came into the world when Adam and Eve sinned. This is why "creationists" like myself believe that the evidences used by evolutionists to theorize an evolutionary advance of life is wrongly interpreted. If evolution were the way that life came into the world then the garden would have been planted on a billions-of-years-old graveyard that also contained the parents of Adam and Eve. Death would already have been present, so what kind of a hollow warning would it have been for God to tell Adam and Eve, "don't sin or you will die"? Did they not expect to die anyway? So much for paradise.
I know that you have come to believe that the evolutionary scientists have "proven" that life came about naturally over billions of years. In so much as they have convinced you, they have "proven" their case. They have not convinced me, so I continue to consider the evidence of the biblical creation account to be persuasive. It is a matter of faith. Just as the literalness of the flood is a matter of faith.