Great post above. If I may, I have some possible answers to your questions.
Satan falling from the sky is equivalent to what we read in Colossians 2:15 . . . and it is the result of Spiritual Circumcison . . . the removal of the Lord's Curse as defined in Romans 5 and Galatians 3:13 (NLT is best for the latter).
Colossians 2:15 NLT - "In this way, he disarmed the spiritual rulers and authorities. He shamed them publicly by his victory over them on the cross."
So again, by removing the Curse, Satan and his minions are thus defeated in the individual life of a True Believer. The Circumcision of Christ is the single most important concept that we seek and obtain in our entire lives. When Christ mentioned Satan falling as lightning, this was a portion of His discussion with the returned "Seventy" that went out and cast out demons (Spiritual Circumcision) and issued physical healings. So, Satan falling as lightning is a direct correlation to Spiritual deliverance from the devil. Ha! Defeated!
I have literally scoured the entire Bible a few times, making sure that I miss nothing by using multi-colored highlighters, highlighting each thought and concept, logging much of it in an organized, sortable and filterable Excel Database. I don't know that there is any more clear explanation to your question other than these things are all a part of the pre-written Plan of God, all found within the Scroll of the Lord. This Scroll contains all events right down to the lives of owls and falcons. It's pretty incredible. Ephesians chapters 2 3 three provide a shallow outline of the Mysterious Plan of God. And of course, if we read the Bible in a timeline, chronological order, we will get a feel for the real Plan, the True story. I'll never forget my first time through . . . it was incredibly exciting to see how things fold as the events actually happened one after the other. Unbelievable!
I think you're right, in that it this is typically the time of the last ice-age . . . if that's even correct. But, it could be the approximate time of Noah's Flood.
I think that's it. I'd say that it was because of all this released and taught knowledge from the fallen Sons of God, and the subsequent buildings that came from them, that God wiped mankind out. If we recall, God didn't want any monuments or structures built (large ones) because the focus of them would become the objects of "man's" desires, thus we would lose focus and dependence upon God. A near battle within the Israelites broke out because the group that stayed on the originating side of the Jordan built a massive wall. Fortunately, that beef was squashed. However, the giant races re-appeared after the flood which indicates to me that God merely wiped out the flesh of these "Sons of God" and that perhaps some of the spirits remained. Thus, after Noah's sons began to pro-create, the flesh of cursed Ham was introduced to those spirits, hence we have the Seven Nations whom the Lord called to have entirely wiped out. Again, they corrupted humanity and they became abominations.
Sorry, but I'm only giving a general rundown on the above.