The story of the flood is not about a God who kills and destroys, rather about a God who loves, saves, and protects despite the fact that humans were continually and persistently walking away from the path taught by God. 

A good way to read and understand the stories in the Bible is to always remember that the stories were written by people to reflect on their existential reality, which was often hard and cruel, and considered the possible causes of such hardships.

Jesus points out is that there is something within us that has an unavoidable connection to cause and effect. Good trees and bad trees symbolize the state of our mind that is directly related to the quality of our actions. 

God granted the priesthood to Aaron and his sons with the ritual of atonement. This was the removal of all their sins and transgressions, meaning there is no sin that is unremovable, according to the Bible

The story about the serpent and the woman is about our struggle to rise above our physically-oriented perception of reality and our desire to make things our own.