Okay, now I see where you went wrong. Not in your understanding of Romans 4, but who it is about, and WHY. Behold, read this whole post. It is not long, but it can teach you the real spiritual truth behind the Cross and the Blood of Jesus.The reason that Paul told you in Romans 4:8 that God does not charge SIN to the BORN AGAIN...
"Jesus is the ONE TIME Eternal SACRIFICE for all sin".
"God made Jesus to be SIN FOR US".
Jesus is our "sin bearer", and the born again are eternally become = the "Righteousness of GOD, in Christ".
That is the Divine Exchange that happens to a sinner when they Give God their FAITH in Christ.
= "faith is COUNTED BY GOD, as Righteousness".
This is why 2 Corinthians 5:19, explains that sin is gone, because Christ has dealt with it all, 2000 yrs ago on THE CROSS., which is HOW God has reconciled the world to Himself, John 3:16 & John 3:17= per each person, once they give God their FAITH.
And THAT is the "message of reconciliation" that is the Gospel of the Grace of God that you have never yet understood, nor do you care to understand it.
Romans 4 are Old Testament saints that were looking FORWARD to the Messiah, but still had their sin nature, because that can ONLY be cleansed by the BLOOD OF JESUS when He died on the CROSS. For instance, in Romans 4 we see David and his confession after Bathsheba. Because of their confession and repentance their sins were not charged to them and as Romans 3 points out, God OVERLOOKED their sin. THAT is why they were not charged with their sin, Behold! See this doctrine changing correction from before Christ, to after Christ.
Look at the chapter before. If you had read that, then you wouldn't have gotten an OLD TESTAMENT account, and misapplied it to the New Covenant, and created a heresy.
21 But now the righteousness of God apart from the law is revealed, being witnessed by the Law and the Prophets, 22 even the righteousness of God, through faith in Jesus Christ, to all and on all who believe. For there is no difference; 23 for all have sinned and fall short of the glory of God, 24 being justified freely by His grace through the redemption that is in Christ Jesus, 25 whom God set forth as a propitiation by His blood, through faith, to demonstrate His righteousness, because in His forbearance God had passed over the sins that were previously committed, 26 to demonstrate at the present time His righteousness, that He might be just and the justifier of the one who has faith in Jesus.
Behold, the blood of bulls and goats only covered sin, but it looked forward to the true substance of their sacrifices. Only the blood of Jesus TAKES AWAY our sins. 1 John 3:5
You also have a common misinterpretation of God's GRACE. It is not a cover up of sin as you appear to believe. Compare what scripture says about the gospel. We know the gospel to be about God's grace, not law.
16 For I am not ashamed of the gospel of Christ, for it is the power of God to salvation for everyone who believes, for the Jew first and also for the Greek. 17 For in it the righteousness of God is revealed from faith to faith; as it is written, “The just shall live by faith.”
But none of these things move me; nor do I count my life dear to myself, so that I may finish my race with joy, and the ministry which I received from the Lord Jesus, to testify to the gospel of the grace of God.
So you see, grace is the power of God in us to actually BE righteous ourselves. In the Old Testament such as Abraham, righteousness was merely "Imputed." Now, with Christ living INSIDE of us, our righteousness is real. Christ lives through us, so we are FREE FROM SIN.