[Hermann the Cherusker]

For example, if +Augustine had been able to read Greek and had read the works of the Greek Fathers, would he have come up with the doctrine of Original Sin, something different from what the Greek Fathers had taught?

St. Augustine cited a number of Greek Fathers when discussing that very topic.

But the Catholic arguement is simplest when reduced to its basic terms. In the creed, we "confess one Baptism for the remission of sins". We Christians have always baptized infants. Ergo, we are baptizing them for the remission of sins, when they have as of yet comitted none of their own, with a rite which includes exorcisms that obviously presume the unchristened child is under the power of the devil.

But really, you seem to think as though St. Augustine were acting in a vacuum. All the while that St. Augustine was refuting the heretics, he was receiving copious support from other Churches, and especially from Rome, where Popes such as Zozimus and Boniface acted upon St. Augustine's condemnations and expelled heretics like Julian of Eclanum from the Church. If St. Augustine were saying thing that the rest of western Christendom did not believe, then he certainly had the whole lot of them quite fooled, given his near unanimous support in Africa, Italy, and elsewhere, and the quick acclimation of the genius of his works after his death.

What would a council do with the Dictatus Papae?

Why must it do anything? This is not a dogmatic document.

while we are really quite content with the status quo

How can one be content with violating the will of the Lord that "all may be one"?

I'm not content at all about the situation of division.

[Destro]

As far as I understand it the original sin is the fall of Adam - we who come from Adam live under the consequences of their original sin (not ours). Think of it as a landlord kicking out unruly tenants but will invite them back in if they agree to behave by the rules. Baptism is an initiation ritual - only after baptism can sins be forgiven. We are not painted guilty by original sin only live in the world created as a result of that original sin. Christ was the way to correct Adam and Eve's error. The way of reconciliation between God and the offspring of Adam and Eve.