Sons of God, daughters of men? The Bible is full of abbreviations, just like we use when texting. “Sons of God” refers to men who were more or less honest about dependence and conscious of the image of God. “Daughters of men” refers to women who were not honest about dependence. The power of evil is often portrayed by the seductive woman (Proverbs 9).
Where did dinosaurs come from and where did they go? Consider any of the animals we know of, especially reptiles (and bats), if they continued to grow in size and violent nature for hundreds of years? As with people, so with animals: a shorter life span puts a limit on how large and violent a person or animal can be, and still there are Goliaths from time to time, maybe as a reminder?
God’s grief does not mean He regrets His own failure in creation nor that He wishes He hadn’t created in the first place; both are impossible because God knows everything. God is grieving as we do sometimes when the way things have to be are grievous. Women have grief in childbearing; parents have plenty of grief as good, faithful parents. But grief it is.
The flood is parabolic (see 1 Peter 3:21). An essential though partial remedy for the human condition is to keep it immersed in the Word of God, the living water that impresses truth upon us.