All have sinned and fallen short of the glory of god
This is the truth, every man is a sinner because every man has committed his own personal sin.
david said that in Sin he was created
This is also true, but David did not say he was born a sinner, you are reading that into the text. The Jews who had these scriptures for 1500 years before Augustine NEVER interpreted these scriptures to teach Original Sin. This is historical FACT.
paul said that in Adam, ALL have sinned, as god reckoned His transgressions unto ALL who would follow after Him!
Pure falsehood, the scriptures NEVER say that all men have sinned in Adam.
Could man be saved by keeping the law than?
If a man kept the law he would have no need of being saved, as he would not be lost. Jesus is the only man who has ever perfectly kept the law.
How did jesus avoid sinning, was it due to his 'free will" response to sin?
He obeyed the word of God just like we do, except he did it ALL the time. We don't, we often disobey and sin. We are not forced to sin, we choose to.
Jesus seems to imply that he could have sinned.
Jhn 8:55 Yet ye have not known him; but I know him: and
if I should say, I know him not, I shall be a liar like unto you: but I know him, and keep his saying.
Jesus said "IF" he should deny that he knew his Father he would be a liar. The word "IF" denotes possibility. Why would Jesus suggest it might be possible he could commit sin if he were unable?
Could we NOT ever sin as he did, since to you both him and us were the same in our humanities at birth?
No man ever has to sin. That said, no man but Jesus has ever lived his entire life without sinning, except little children or babies who have died before they could commit sin. But no man who has matured and understood right from wrong has failed to sin.
Why is it offensive to believe men are born upright? This does not rob Jesus of being Saviour, Adam and Eve were made upright, they sinned, and they needed a Saviour. It is the exact same for all men.
Scripture says God has made man upright, and it is speaking of all men, not just Adam.
Ecc 7:29 Lo, this only have I found,
that God hath made man upright; but
they have sought out many inventions.
All this false doctrine in the church like the Immaculate Conception, baptizing babies, Purgatory, all because Augustine did not know the scriptures and introduced the teachings of the Manicheans into the church who believed all matter was evil. The Jews never believed the scriptures taught Original Sin, neither did the Eastern church that used only Greek texts. This is historical fact.