What should Constantine or the Church have done?

[Philip_B]

I agree that Eastern Churches would also maintain the NT too. As I remember the split did not happen until around 1054? correct. Thus would the Eastern Churches also be considered Catholic up to that time? We would also have Jewish Scholars, educated maintaining the Hebrew Scriptures.

The Great Schism is generally marked by the service of the Bull of Excommunication from a dead Pope on the 16th on July 1054, during the celebration of the Holy Eucharist in Hagia Sophia, Constantinople. so on that point you are correct.

The Eastern Churches, aka The Orthodox Churches, have always been considered Catholic, not only up to that time but also since that time right up until today. Catholic is one of the four notes of the Church, as expressed in the Creed, that expressed the faith of the whole Church, of the 1st Council of Constantinople in 381 AD.