You have made a fatal blunder.
Your understanding of the revelation of Jesus Christ is missing in your posts.
I have not neglect that. In Matthew 4:15-23, Christ began his ministry with the Gospel message to repent for the Kingdom of God is at hand, which was a light to the Gentiles, and the Mosaic Law was how his audience knew what sin is (Romans 3:20), so repenting from our disobedience to it is a central part of the Gospel of the Kingdom. Christ also set a sinless example for us to follow of how to walk in obedience to the Mosaic Law and as his followers we are told to follow his example (1 Peter 2:21-22) and that those who are in Christ are obligated to walk in the same way he walked (1 John 2:6). In Titus 2:14, Christ gave himself to redeem us from all lawlessness and to purify for himself a people of his own possession who are zealous for doing good works, so becoming zealous for doing good works in obedience to the Mosaic Law is the way to believe in what Jesus spent his ministry teaching by word and by example and in what he accomplished through the cross (Acts 21:20) while returning to the lawlessness that he gave himself to redeem us from is the way to reject everything that he accomplished.
The law gave Israel a knowledge of sin but not the ability to obey that law.
In Romans 10:5-8, it references Deuteronomy 30:11-20 as the word of faith that we proclaim in regard to proclaiming that God's law is not too difficult for us to obey and that obedience to it brings life and a blessing while disobedience brings death and a curse, so choose life!
[quoteJesus Christ is the only way to achieve righteousness.[/quote]
Agreed.
[quoteWe receive the righteousness of Jesus Christ, a perfect righteousness, and that was a gift.[/quote]
To have a character trait means to be a doer of that trait, so for God to be righteous means that He is a doer of righteous works and the receiving the gift of righteousness through faith means receiving the gift of becoming a doer of righteous works in obedience to God's law through faith..
You cannot obey the rules of the law because that was not the purpose of the law.
The purpose of God giving commands is straightforwardly for us to obey them.
It's not about you or your failure to obey the law, it never was about you.
You will boast in Jesus Christ and never boast in yourself, ever again.
God did not give the gift of His law for the purpose of giving us something to boast about, but to teach us how to boast in Christ. God did not command good works in order to establish our own goodness, but to testify about God's goodness, which is why our good works in obedience to the Mosaic Law give glory to Him (Mark 5:16). Moreover, by testifying about God's goodness, we are also expressing the belief that God is good, or in other words, we are believing in him, and the same goes for God's other character traits, so the way to believe in God is by being a doer of His character traits in obedience to the Mosaic Law.