As it happens hashmayem is plural and heavens is correct.
In2 Cor 12:2
2 I knew a man in Christ above fourteen years ago, (whether in the body, I cannot tell; or whether out of the body, I cannot tell: God knoweth
such an one caught up to the third heaven.
KJV
Paul speaks of the third heaven; so the KJV is contradicting itself by your standard but not in fact.
Gen 2:1-4
2 Thus the heavens and the earth were finished, and all the host of them.
2 And on the seventh day God ended his work which he had made; and he rested on the seventh day from all his work which he had made.
3 And God blessed the seventh day, and sanctified it: because that in it he had rested from all his work which God created and made.
4 These are the generations of the heavens and of the earth when they were created, in the day that the Lord God made the earth and the heavens,
KJV
Is the KJV fake too now?