The word "nephal" means "tyrant" and "bullies" which is the result of covenant human sons of God who were unequally yoked with non-covenant women and their children grew up without restraint and without law.
Sorry, haven't found your analysis of anything in scripture, to be accurate.
Satan cast his demons down to earth after seducing Eve, and then Adam to sin:
3 And another sign appeared in heaven: behold, a great, fiery red dragon having seven heads and ten horns, and seven diadems on his heads.
4 His tail drew a third of the stars of heaven and threw them to the earth. And the dragon stood before the woman who was ready to give birth, to devour her Child as soon as it was born. (Rev. 12:3-4 NKJ)
He tried to corrupt God's image in man with the image of angels, that's what the Nephilim were doing in the war against the "woman's seed" Christ (Gen. 3:15).
Because humanity was pissed off God forbade them access to immortality (Gen. 3:22-24; 6:3, 5) they conspired with Satan and their daughters forced the Watchers to see pornography 24/7 until they were seduced to leave their proper habitation and also take human wives:
1 Now it came to pass, when men began to multiply on the face of the earth, and daughters were born to them,
2 that the sons of God saw the daughters of men, that they were beautiful; and they took wives for themselves of all whom they chose.
3 And the LORD said, "My Spirit shall not strive with man forever, for he is indeed flesh; yet his days shall be one hundred and twenty years." (Gen. 6:1-3 NKJ)
They thought unfallen angels (immortal) would sire human children also immortal. Perhaps they did, but its moot because all died in the flood:
21 And all flesh died that moved on the earth: birds and cattle and beasts and every creeping thing that creeps on the earth, and every man.
22 All in whose nostrils was the breath of the spirit of life, all that was on the dry land, died.
23 So He destroyed all living things which were on the face of the ground: both man and cattle, creeping thing and bird of the air. They were destroyed from the earth. Only Noah and those who were with him in the ark remained alive.
(Gen. 7:21-23 NKJ)
Satan's angels trapped on earth (God wouldn't permit they reenter heaven) died physically, the "spirits of demons" (πνεύματα δαιμονίων Rev. 16:14 BGT) went to the Abyss. The angelic sons of God didn't join Satan's rebellion, they sinned by having sex with strange flesh. They are in Tartarus, not the Abyss with Satan's demons:
6 And the angels who did not keep their proper domain, but left their own abode, He has reserved in everlasting chains under darkness for the judgment of the great day;
7 as Sodom and Gomorrah, and the cities around them in a similar manner to these, having given themselves over to sexual immorality
and gone after strange flesh, are set forth as an example, suffering the vengeance of eternal fire.
(Jude 1:6-7 NKJ)
The "men of renown", hybrid angel human offspring of both the Nephilim and sons of God, who wouldn't believe Noah's preaching God would forgive their "Frankenstein nature", went to a special prison because they weren't evil, just not able to believe Noah's preaching.
As for the wicked "men of renown", when they died they became the "unclean spirits" who are subordinate to demons, roaming the earth seeking corporeality by possessing insects, animals and men.
As for the Nephilim who weren't permitted to return to heaven, but who didn't have sex with women, these also died in the flood and the disembodied "demons" also roam the earth possessing insects, animals and men and some amuse themselves by making existence miserable for the lesser "hybrid angel-human" unclean spirits.
The angel of God shone the light on the earth revealing all these things to those with eyes to see, who believe the Scriptures and all that is written. These unclean spirits and demons infest Christendom and all the world's false religions inspiring all sorts of evil:
1 After these things I saw another angel coming down from heaven, having great authority, and the earth was illuminated with his glory.
2 And he cried mightily with a loud voice, saying, "Babylon the great is fallen, is fallen, and has become a dwelling place of demons, a prison for every foul spirit, and a cage for every unclean and hated bird! (Rev. 18:1-2 NKJ)
Jesus revealed all this to His disciples:
31 Another parable He put forth to them, saying: "The kingdom of heaven is like a mustard seed, which a man took and sowed in his field,
32 "which indeed is the least of all the seeds; but when it is grown it is greater than the herbs and becomes a tree, so that the birds of the air come and nest in its branches."
33 Another parable He spoke to them: "The kingdom of heaven is like leaven, which a woman took and hid in three measures of meal till it was all leavened."
34 All these things Jesus spoke to the multitude in parables; and without a parable He did not speak to them,
35 that it might be fulfilled which was spoken by the prophet, saying: "I will open My mouth in parables; I will utter things kept secret from the foundation of the world."
(Matt. 13:31-35 NKJ)