Moving on through the OP, let’s look at that definition of “sin”. The Hebrew for that in Genesis 4:7 and throughout the period before and after the Law of Moses is chatta’ah. Since there was no law yet, it couldn’t mean more than it meant, “offense” or “lack” and other similar definitions. It meant any failure that offended the offender or offended, whether God had entered into the subject or not. It could be as slight as slapping a friend on the back causing him to spill some coffee on himself. Simple accidents can offend, many are instantly forgiven.
The Law made sin more sinful, according to Paul. It put in writing judgments from God concerning behavior that directly offends him. The only way to come out from under that enhancement of sin (a list of definitions of serious offenses) was to die. Once a person dies he is free from the Law. But while alive it is the Law that teaches people what sin is.
Let me jump to how being “in Christ” relates to that. Jesus died, being freed from the Law as was proper for any other Jew. But in his case he was resurrected, thereby walking alive after being freed from the curse of the Law. The Bible makes it clear that when a person believes on and trusts in Jesus for salvation, he too dies spiritually to that old Law, raising up alive with Jesus in baptism, walking untouched by the Law. He then walks under the new law of Christ, that of love. In that way keeping of the Law isn’t what determined our eternal destiny. Instead, it is our faith, our abiding trust, that Jesus paid all that was due toward the Law, in Himself, for every follower. That cost him his blood. The Greek word for sin, hamartia, points to the same offenses the Jews knew, but breaking them isn’t what consigns people to hell. Unbelief does. The reason is Jesus’ blood washes believers of the stain of sin. Without leaning on that blood there is no hope for a sinner. Without the Spirit in us it is impossible not to sin. Separated from God there can be no forgiveness of sin, because unbelief leaves a person a slave to sin, a child of the Devil. God gained legal access to every human to revel himself at least once, seeing Satan enjoys such access. But more importantly, men whom God awarded dominion over earth, have spoken to “authorize” intervention from God. He might visit just once in a lifetime, offering salvation based on the hearing of a single verse of scripture, giving that person but one chance to accept his offer.
How do I relate to he Law? I love the Law. It teaches me not to hate. But most of us probably grew up under a large list of “Dont’s”, without a comparable lists of “Do’s”. Jesus fills that gap with ways to love, curiously avoiding emphasis on Dont’s. Once Love is strong in us we will tend to not choose to be evil, unlike our situation before salvation, too comfortable with sin, whether sinning or witnessing it. As a result I am very careful over what I view, not caring to watch movies where a murderer kills, a rapist rapes, or an affair is underway. What apparently was entertaining, watching endless sinning, has become disturbing to me. My viewing habits exclude episodes of sin behavior. That increased my blocks of quality time to spend with loved ones, to enjoy my labors, to help neighbors, to minister to needs, to learn to cook healthy meals of real food, to study the Word, pray, and engage in more satisfying recreation. I don’t think about sin. I am always meditating over scriptures, witnessing to folks. I don’t have a checklist of Moses’ laws on the refrigerator.
Again, what about holy living is more evil than living as an unbeliever? What is wrong with teachings about love and righteousness (right-standing before the holy God)?