Some thoughts...
Regarding Rev 12
I think we need to be very cautious about making any dogmatic statements regarding the meaning of the symbolic language in Rev 12.
I agree with Heiser that the war in heaven between Michael and the Dragon (Rev 12:7-9) takes place after the birth of Christ.
However John's vision does not provide a specific context for when the Dragon swept a third of the stars out of the sky in Rev 12:3-4. The events of Rev 12:3-4 appear to take place sometime before the birth of the child (Jesus) in Rev 12:5.
So I think the text of Rev 12 indicates that the Dragon sweeping a third of the stars out of the sky (Rev 12:3-4) and the war between Michael and the Dragon (Rev 12:7-9) are two separate events... one takes sometime before the birth of Jesus, and one takes place sometime after the birth of Jesus.
Regarding 2 Peter 2:4
Heiser asserts that there is no Scriptural candidate other than Genesis 6:1-4 for the event that Peter refers to in 2 Peter 2:4.
I partially agree with Heiser. But I am convinced that there is no scriptural candidate for Peter's reference in Genesis 2:4 at all.
However, as I have discussed at length elsewhere, there are a number of reasons that Gen 6:1-4 is not a Scriptural candidate either.
Off the top of my head...
- Genesis 6:1-4 doesn't mention angels.
- Nowhere in Scripture does the phrase "sons of God" refer to fallen angels in rebellion against God.
- A key component of Peter's description of the event in question, "but sent them to hell, putting them in chains of darkness to be held for judgment", is totally absent from Genesis 6:1-4.
- In Genesis 6 God punishes the sin of humans not angels. Which indicates that Genesis 6:1-4 is not the Scriptural basis for the event Peter references in 2 Peter 2:4.
All that to say this... I think we need to be very careful about making claims about how or when the angels who follow Satan fell. I would assume it took place in conjunction with the fall of Satan (which pre-dates Adam), but I can't know that for sure.