Job,
1:8 Then the Lord said to Satan, “Have you considered my servant Job?
There is no one on earth like him; he is blameless and upright, a man who fears God and shuns evil.”
Is Job righteous by work or by faith?
Does Job need Jesus' grace of Salvation?
Did Job follow Moses's Law 100% and faultless?
Righteousness is a character trait of God that is straightforwardly expressed by doing what is righteous and the Law of Moses is God's instructions for how to express that character trait, not for how to attain it. For example, the Law of Moses reveals that helping the poor is a way to do what is righteous, but no amount of helping the poor will ever cause someone to become righteous because the one and only way that there has ever been to become righteous is by grace through faith. In Romans 3:21-22, it does not say that the Law and the Prophets testify that the righteousness of God comes through 100% faultless obedience, but rather they testify that it comes through faith in Christ for all who believe, so that is the only way to become righteous that is testified about in the Law and the Prophets. Having a character straightforwardly means that we are someone who chooses to take actions that express that character trait, so when God declares us to be righteous, He is also declaring us to be someone who chooses to take actions that express His righteousness in obedience to His instructions for how to do that found in His law.
So someone who has faith is also someone who chooses to take actions that express faith, which is why there are many verses that connect our obedience to God with our faith in Him, or that connect our disobedience to God with breaking faith. For example, in Romans 3:31, our faith upholds the Law of Moses. In Matthew 23:23, Jesus said that faith is one of the weightier matters of the Law of Moses. In Revelation 14:12, those who kept faith in Jesus are the same as those who kept God's commandments. In John 3:36, believing in Jesus is equated with obeying him. In James 2:17-18, faith without works is dead and he would show his faith by his works, so doing good works in obedience to God is what faith looks like. Every example of faith listed in Hebrews 11 is also an example of works done in obedience to God.
In Psalms 119:29-30, David wanted to put false ways far from him, for God to be gracious to him by teaching him to obey the Law of Moses, and he chose the way of faithfulness, so this has always been the one and only way of salvation by grace through faith. In Exodus 33:13, Moses wanted God to be gracious to him by making known to him His ways that he might experientially know Him, and Israel too, in verses like Deuteronomy 10:12-13, Isaiah 2:2-3, Joshua 22:5, Psalms 103:7 an Psalms 119:1-3, God made known the way to experientially know Him through His law, and in John 17:3, eternal life is experientially knowing God and Jesus, so again that is the one and only way of salvation by grace through faith. In Titus 2:11-14, our salvation is described as being trained by grace to do what is godly, righteous, and good, and to renounce doing what is ungodly, which is what the Law of Moses was given to teach how to do, so God graciously teaching us to obey it is itself part of the content of His gift of salvation.