Where did God ever call pre-adamic sub-terrestrials “the Sons of God”?
that is a very bold speculation you are making there.
For what reason?

Genesis 6:2
the hebrew says “Bene Elohim”
I think you already know what that means.

Why are you trying to come up with novel interpretations of holy scripture?
God needed a loophole to crush Satan?
Then why is it that when Satan broke the loophole;

Adam was punished,
the earth was delivered over to the dominion of the devil
and God sent His only begotten Son to crush the head of the serpent, and redeem mankind who had sold himself for nought?

stop trying to apologize for things beyond your ken.
“Every Good gift, and every perfect gift, comes down from above, from the Father of lights, in whom is neither variableness, nor shadow of turning.
Of His own will begat He us of His word of truth, that we might be a kind of first fruits of His creature”

Does God need 6 advents to create mankind?
Or did YHWH Elohim say from the beginning “Let us make mankind in our image, and after our likeness…”
as for the “Sons of God”

they are not like Christ Jesus;
because in pride they broke the bounds of their habitation,
whilst the Son of man in humility exalted the glory of Our Father which art in heaven.

Philippians 2:1-13
If there be therefore any consolation in Christ, if any comfort of love, if any fellowship of the Spirit, if any bowels and mercies, Fulfil ye my joy, that ye be likeminded, having the same love, being of one accord, of one mind.
Let nothing be done through strife or vainglory; but in lowliness of mind let each esteem other better than themselves.
Look not every man on his own things, but every man also on the things of others.

The Attitude of Christ

(Isaiah 52:13-15)

Let this mind be in you, which was also in Christ Jesus:
Who, being in the form of God, thought it not robbery to be equal with God:
But made himself of no reputation, and took upon him the form of a servant, and was made in the likeness of men:
And being found in fashion as a man, he humbled himself, and became obedient unto death, even the death of the cross. Wherefore God also hath highly exalted him, and given him a name which is above every name:
That at the name of Jesus every knee should bow, of things in heaven, and things in earth, and things under the earth;
And that every tongue should confess that Jesus Christ is Lord, to the glory of God the Father.

Shining as Stars

(Matthew 5:13-16)

Wherefore, my beloved, as ye have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling.
For it is God which worketh in you both to will and to do of his good pleasure.