The Kingdom of God and the Kingdom of Satan

As many Christians have said in the past, sin comes from three arenas: the world, the flesh, and the devil. This is a very helpful way to balance out the three arenas where we are tempted. In the Reformed tradition, it appears that the flesh, our own sinful nature, is the primary source for our sin, and it is important to balance this with the other two areas. In thinking about it more, though, I am coming to see that sin is actually primarily under the arena of lordship, and hence Satan is the primary source of our sin.
All unbelievers are under the lordship of Satan under his kingdom. The kingdom is composed of the world, which consists of all unbelievers, and of which all Christians also were once a part. In fact, the Bible says that all of these people are the children of Satan. These people live like their father and serve him.
When Christ brings people under submission in a triumphal procession of enslavement and submission (2 Corinthians 2:14), then we are now under the lordship of Christ. We are adopted by a new and good Father, the Father of lights. Our body of flesh in submission to the world has been removed (Colossians 2:11) by Christ. The problem is that believers are still dwelling in the world that is dominated by Satan and by his followers.
Additionally, our own flesh, while new positionally in Christ and being transformed by the Holy Spirit, still longs in some way to be under the dominion of Satan. We sometimes look back to our old father, and are tugged by our old family. This is a terrible thing, and one of the many reasons why believers desire for heaven more and more every day.

Who are the Nephilim?

A vexing question in the study of the book of Genesis is the identity of the Nephilim. After careful study, I think that they are people who are the illicit product of sexual union between angels and women. Though Genesis 6 does not provide enough information to be positive of this identity, there are two key items that lead to this understanding.
First, “sons of God” (benai-ha-elohim) in Hebrew is only used outside of Genesis 6:2 and 4 in Job 1:6 and 2:1. In Job, it refers to angels, and Satan is among them. Job 38:7 has almost the exact same statement (benai-elohim), and this is the clearest indicator that “sons of God” refer to angels. Interesting, the only other place that the ESV has “sons of God” in the Old Testament is in Deuteronomy 32:8. In the Hebrew, it says “sons of Israel.” In the LXX, it says “angels of God.” Job 1:6 and 2:1 both say “angels of God” in the LXX, and Job 38:7 has “my angels
Second, the New Testament teaches that angels had illicit sex. Jude 1:4-8 is very important for this. It says that “the angels who did not stay within their own position of authority, but left their proper dwelling ….. just as [did those] which likewise indulged in sexual immorality and pursued unnatural desire.” 2 Peter 2:1-9 is a clear parallel to this. Both compare the angels who sinned to the sexual immorality of Sodom and Gomorrah, and the “just as” and “which likewise” in Jude I think necessitates that both sins were regarding sexual immoral and unnatural desire.
I believe that the primary reason why this view is rejected is because of a general anti-supernatural belief that permeates our society today. This view dramatically affects one's understanding of the corporal nature of angels, and it also affects the timing of when a number of angels "fell."