"Mother of God" is a statement about Jesus, not about Mary. As per the Council of Ephesus, Mary being called "Mother of God" or "God-bearer" (the latter of which being a slightly more literal meaning of the Greek word
Theotokos) is a defense of Jesus' Divinity. As Jesus is both true God and true man, it is therefore proper to call Mary the Birthgiver of God. Not that God the Son did not exist prior to the Incarnation, but that He continued to be God even while becoming incarnate.
Yeah, you can blame that one on Scholastic theology. The Orthodox don't have a unified opinion. We hold that Mary is immaculate and sinless, but exactly when she
became such is another matter. Some say it was at the Annunciation, some say it was from her birth onward.
We only call Mary "Queen of Heaven" because she is a co-heir with Christ, Who sits on the throne of the New Jerusalem. All of us will be "kings [or queens] and priests" (Revelation 5:10), and co-heirs with Christ (Romans 8:16-17)
"The prayer of a righteous man avails much" (James 5:16).
It's not that Mary's a sort of goddess or has some "stuff" that the rest of us don't have, it's just that she is a righteous and holy person, sanctified by God, as we all will one day be.
It may not be monotheism
as you believe it, you may not like the rationale and the explanation given, but the Trinity is a monotheistic belief. Trinitarians are monotheists, and all our Fathers have stated as much.
Even if you personally think the Trinity equates to "three separate gods", this is a misrepresentation of what we believe and teach. I say this not to convince
you of anything, but to set the record straight for those who may be reading and don't know what the Trinity is.
St. Gregory of Nyssa said in his
On the Holy Trinity, and on the Godhead of the Holy Spirit:
"They charge us with preaching three Gods, and din into the ears of the multitude this slander, which they never rest from maintaining persuasively. Then truth fights on our side, for we show both publicly to all men, and privately to those who converse with us, that we anathematize any man who says that there are three Gods, and hold him to be not even a Christian."
Outside the fact that tritheism is roundly denounced by all the Fathers. St. Gregory of Nyssa even has an entire treatise dedicated to this called
On "Not Three Gods". Christians are not and have never been polytheists. I have made you aware, so please stop misrepresenting what we believe, willfully or otherwise.
This is not a debate forum, so I won't press the issue further, only to state that we wrote our New Testament and know what we meant by it. The people who defended the dogma of the Trinity at Nicaea, and the divinity of both the Son and the Holy Spirit throughout the centuries leading up to it, were reading the New Testament in the language in which it was written, and were aware of all its nuances. They were brought up in the teachings of the Apostles, guided by teachers who were appointed by these same Apostles. If the Trinity is a lie, then so is the New Testament.