Question: "Why does Orthodoxy teach that one must have perfect Nicene Christology in order to be saved, when the earliest Hebrew Christians did not have the Christology as articulated by the Councils of Nicea and Chalcedon? According to Nicea, many of the earliest Hebrew Christians would be heretics, as well as several Church Fathers, since they were subordinationists. We cannot even speak of a dogma of the Trinity until the Council of Constantinople."
The Church teaches perfect Nicene Christology, but I don't believe that the Church teaches that any individual has to have a perfect understanding of that Christology in order to be saved. There are many people who lack the intellectual capacity to have a perfect understanding of Orthodox Christology or Trinitarian theology. We should certainly try to understand these things as well as we can, but being saved is not the ability to pass a pop-quiz on theology. Someone can be saved even if they have demonstrably erroneous beliefs, but erroneous beliefs can lead one off the path of salvation, which is why the Church strives to correct such people. However, it is only when someone refuses to be corrected by the Church that they cut themselves off from the Church, which is the Ark of Salvation. For more on this, I would suggest reading "Christianity or the Church?" by the New Martyr Hilarion (Troitsky).
I am not sure which Church Fathers are alleged to have been subordinationists, but prior to the Church clarifying a doctrine, you often find those in earlier times who use imprecise language, but this does not mean that they held heretical views. But even if some of them did have opinions that were later clarified to be heretical, they clearly did not reject the correction of the Church on the matter.
As for the "Hebrew Christians" that are referenced, this probably refers to the Ebionites, and they were in fact a heretical sect. Most of the early Christian centers had a very strong Jewish core during the time of the Apostles, and those Hebrew Christians remained part of the mainstream of the Church.
The word "Trinity" does not occur in the New Testament, but the doctrine is taught there. One thing that the Jews were very clear on by the time of the New Testament is that God was one (Deuteronomy 6:4). And yet in the New Testament, we are told repeatedly that Christ is God (e.g., John 1:1; John 8:58; John 20:28), and we are told to baptize in the name (singular) of the Father, Son, and Holy Spirit (Matthew 28:19). So clearly, the Church has always taught that God was one, in one sense; and three in another sense. The Church only defined how this was so in greater detail because it was necessary to correct heresies that arose. The Faith of the Church was once delivered unto the saints (Jude 3), and so we reject the idea that our faith has changed, or been added to since the time of the Apostles. But our teachings about the faith have certainly become more precise over time, when the need to correct new heresies has made this necessary.
The earliest surviving use of the word "Trinity" (in Greek Τριάδος) is in the writings of St. Theophilus of Antioch, from a work written in about 180 a.d. (Apologia ad Autolycum 2:15). Though this is the first documented use of the term, it is used in such a way that would suggest it was not being freshly coined, and so probably was in use well before then... but in any case, the fact that the bishop of such an import center of early Christianity would use the term without any hint of it being controversial, shows that it was considered completely consistent with the faith that proceeded his time. St. Theophilus became bishop of Antioch in 169 a.d., and if we assume that he was at least 30 years old by that time, that means he would have come of age when those who knew the Apostles were still very much present in the Church.
We are not saved by having correct doctrine, or having a perfect grasp of the teachings of the Church. We are saved by grace through faith that works by love (Ephesians 2:8-10; Galatians 5:6; James 2:24). But having love does mean that we have to have the humility and love for the Church that inspires us to strive to conform ourselves to the teachings of the Church, and not think ourselves wiser than the Apostles and Fathers who have passed on the faith to us. And whether or not we ever come close to understanding the doctrine of the Trinity perfectly, if we are fully and faithfully united with the Church, the Church (which does understand this doctrine perfectly) will guide us safely along the path of salvation.
See also:
Does Doctrine Matter?
The Doctrine of the Trinity