The fact God's law was never given as a means of earning our righteousness does not mean that we aren't still obligated to obey it for the goals for which it was given.
In Deuteronomy 30:11-20, it says that God's law is not too difficult to obey and that obedience to it brings life and a blessing while disobedience brings death and a curse, so choose life! Furthermore, Romans 10:5-8 references this passage as the word of faith that we proclaim and there are many other verses that repeatedly say that obedience to God's law is the way to be blessed.
Paul never spoke about being free from God's law, but he did speak about being free from sin, which is the transgression of God's law. The bottom line is that we must obey God rather than man, so if you think that Paul spoke against obeying God's law, then you should be quicker to disregard everything that he said than to disregard anything that God has commanded, though the reality is that Paul was a servant of God who never spoke about being free from God's law.
Is it your view that in the OT, the devil had the role of deceiving us into disobeying God?, but in the NT the devil has the role od deceiving us into obeying God? That's absurd.
Self-righteosness does not involve relying on anyone else, so it is contradictory to think that we can become self-righteous by relying on what God has instructed. If God is legalistic for giving the law as a gift to His people and Jesus is legalistic for setting a sinless example for us to follow of how to walk in obedience to it, then we should all be legalistic, but that is not what it means to be legalistic.
In Titus 2:14, it does not say that Jesus gave himself to free us from God's law, but in order to free us from all lawlessness and to purify for himself a people of his own possession who are zealous for doing good works. So the freedom that we have in Christ is the freedom from sin, not the freedom to sin.
