That Noah had already found grace in the eyes of the Lord, was a just man and a preacher of righteousness and walked with God before he built the ark is a key issue of the heart. (Genesis 6:8-9; 2 Peter 2:5)
Well, that was certainly not the case for Noah, so your argument is moot.
You put a lot of faith in man's performance and self-preservation and no faith in God's preservation. (Psalm 37:28; Jude 1:1) You also seem to underestimate the grace of God which operates sovereignly in the lives of believers.
1 Corinthians 15:10 - But by the grace of God I am what I am, and His grace toward me did not prove vain; but I labored even more than all of them, yet not I, but the grace of God with me.
2 Corinthians 1:12 - For our proud confidence is this: the testimony of our conscience, that in holiness and godly sincerity, not in fleshly wisdom but in the grace of God, we have conducted ourselves in the world, and especially toward you.
2 Corinthians 12:9 - And He has said to me, "My grace is sufficient for you, for power is perfected in weakness." Most gladly, therefore, I will rather boast about my weaknesses, so that the power of Christ may dwell in me.
Choosing to believe the gospel is the act of obedience that saves. (Romans 1:16; 10:16)
We have access by faith into grace.. (Romans 5:2) Choosing to place our faith in Jesus Christ alone for salvation (choosing to believe the gospel) is the act of obedience that saves. No amount of works can save you. Romans 5:19 - For as by one man’s disobedience many were made sinners, so also by one Man’s obedience many will be made righteous. You need to look to Jesus and not to self for salvation. (1 Corinthians 1:18-21)
Don't confuse "faith only" per James 2:24 (empty profession of faith/dead faith that produces no works - James 2:14) with faith that trusts in Jesus Christ alone for salvation and not in works. (Romans 4:2-6; Ephesians 2:8,9; Philippians 3:9) Those who have been saved by grace through faith are saved FOR good works and NOT BY good works. (Ephesians 2:8-10)
OSAS is not foreign to what the NT teaches. (John 6:38-40; 10:27-30; Romans 8:30-39; Romans 11:29; 2 Corinthians 1:22; 2 Corinthians 5:5; Ephesians 1:13-14; Ephesians 4:30; Philippians 1:6; 1 John 2:19; Jude 1:1)
Faith that never obeys at all is not genuine faith. In James 2:14, we read of one who
SAYS/CLAIMS he has faith but has
no works (to
evidence his claim). That is not genuine faith, but a
bare profession of faith. So, when James asks, "Can
that faith save him?" he is saying nothing against genuine faith, but only against an
empty profession of faith/dead faith. So, James does not teach that we are saved "by" works. His concern is to
show the reality of the faith
professed by the individual (James 2:18) and
demonstrate that the faith
claimed (James 2:14) by the individual is
genuine. Simple!
Those who truly are saved are new creations in Christ (2 Corinthians 5:17) are preserved in Christ (Jude 1:1) are sealed in Him with the Holy Spirit of promise (Ephesians 1:13) who is the guarantee of our inheritance unto the redemption of the purchased possession.. (Ephesians 1:14) You could never be obedient enough to take away your own sins and earn your salvation. (Romans 3:23; 6:23)
I can see where NOSAS easily leads a person to conditionally trust in works for salvation, which you obviously do. I can see that you need to repent (change your mind) and
place your faith in Jesus Christ alone for salvation (Acts 20:21; Ephesians 2:8,9) You need to choose to believe the gospel by
trusting in the death, burial and resurrection of Christ as the ALL-sufficient means of your salvation. (Romans 1:16; 1 Corinthians 15:1-4)