Like I said, I do believe the gospel. Please tell me what you believe the gospel IS and also what you believe it means to BELIEVE the gospel. (1 Corinthians 15:1-4)Like I said, you don't understand the gospel. You have knowlege pieces, but not the understanding that puts all of those pieces together.
There's only one thing that saves us: Jesus blood at the throne of God that witnesses of his obedience unto death. That's what sealed the covenant whereby we are saved. There is no salvation apart from this.
If Noah and family had died, Christ would not have been born, and subsequently mankind would have perished. It wouldn't have mattered how righteous Noah was because it wouldn't have been enough to save him.
Do you really believe that God is so small that He would allow a series of events to take place that would prevent Christ from being born and causing all of mankind to perish?
Now Noah found grace in the eyes of the Lord and was a just man which is why God chose him to build the ark. Refusing to build the ark was not an option for Noah who was a true man of faith. (Hebrews 11:7)