You say that you are 'all in' on discussing the lessons of the great flood and Noah's ark, but you don't help me to understand 1, the justice, and 2. the lesson in a new beginning.
Note the format of the story. The author describes the mind of God which is beyond human understanding, so we are reading what conclusions mankind made about the cause of the flood. Take any great disaster. Human beings have this habit of looking back on what they had been doing and what they could have been doing better.
This was not a current day by day account of an event as it happened. It was a description looking back over the event once it was past.
Look at the numbers the author used. Seven is often used to denote completeness; it is a number associated with God. Forty is often used to signify change, renewal, new beginnings. The height of the three decks were the same height as the three levels of the temple. In architecture, this symbolized the underworld, the earth, the heavens.
Based on the story, people weren't throwing up their hands wailing about God killing babies. People weren't arguing whether the flood was local or planet-wide. The story presents a picture of reassurance.
The past was complete and God was in charge. God's ark was there for the salvation of the underworld, the earth, and the heavens. The flood was a time of renewal and for new beginnings. Those who had died in the flood (the underworld) were safe. Those who had survived the flood (but had little) were safe. And the heavens were also safe.
Back then, words were seen to have power, and this power was being misused, leading mankind into disaster. There was one man who listened to God, but did not speak...not until after the flood. And the most righteous of men also brought with him the brokenness of mankind. When Noah finally speaks, it is a curse which causes division on earth....And so we begin again. The themes of the story:
1. Salvation for all (those in the underworld, those on earth, those in heaven)
2. New beginnings
3. Words have power so take care
We can't get any of this from the King James English. We need to study the Hebrew and what Jewish Rabbis have to say about the account. We certainly can't ascertain the meaning of this story by studying modern science and listening to what scientists are saying about the possibility (or impossibility) of a planet-wide flood.