I actually find the scriptures you pointed to contradictory to the actual truth that is we are no longer sinners once we have put our faith in Christ. Just as Abraham was considered as righteous for believing God so are we for believing in his son. The scripture about breaking one law and being guilty of them all is God's way of showing us that we can never earn righteousness on our own and proves that we needed a savior (which we have). Jesus did the work and took away the sins of the world

I don't find them contradictory at all. In the second half of your statement, you describe why it isn't contradictory. So, I'm not sure there is anything else I can add. You have done a very good job of it yourself. We are no longer sinners because God has paid the penalty for our sin. Yet due to our sinful nature we still desire to sin and must strive not to. I don't see that as contradictory.