It is obvious that you don't have any scripture that says Adam's sin is imputed to anyone else, nor that Jesus' righteousness is imputed to anyone else. Through the disobedience of Adam, bringing sin and death into the world, many (not all) were made sinners. Those not yet at an age of accountability for deliberately choosing to do evil were not made sinners. If The were, then the scripture would say, "19 For just as through the disobedience of the one man all were made sinners, so also through the obedience of the one man the many will be made righteous."
How are the many made sinners through the disobedience of Adam? The text does not say. Was it by Adam and Eve, having set off on a path of distrust toward God and trust toward satan, subsequently keeping on setting bad examples for many of their kids, and many of their kids badly training many of their kids? Maybe. Was it that bring in inevitable mortality to mankind through denial of access to the tree of life, humans were more pressured into taking moral shortcuts to avoiding the suffering and maximising the pleasure they would experience before death? Maybe. But it certainly does not say anywhere that they were made sinners by Adam's sin being imputed to them. That is your inference, but not the only possible inference.
You say, "If Adam's sin is not imputed to all his progeny then neither is the Last Adam's perfect obedience imputed to the "many" to make them righteous."
Nowhere are we told that Jesus' perfect obedience is imputed to anyone. When our sins are removed, we become righteous, clean in God's sight, just as clean as Jesus is in God's sight. We do not need to have Jesus' righteous behaviour imputed to us to become and remain righteous before God. Why did you change "many" to "all" regarding the sinner part of the equation in v. 19? There is no warrant for you to do that. You did it just to write your Doctrines of Grease into the biblical text.