I would agree with everything you've said but what was it that made Noah righteous? God gave the instructions and Noah obeyed. God also gave him all the skills and fortitude to help him complete his task. Likewise God gives us our instructions and skills. It is He who bears are fruit.
Noah has apparently done everything God has asked of him thus far. God has said he is now righteous. I find it interesting upon further inspection that God orders him into the ark as a final "command" and then states that he is righteous.
And there is where our responsiblity and volition comes in, obedience.
And faith in Christ is an act of obedience commanded by God. (Jn.6:28-29)