“her faithful and prior understanding that she belonged to God alone, God, the father of her Son.”
This isn’t in Scripture, nor is there evidence it was taught by any Apostle, nor believed by any Christian before 100 ad.
It is made up later, as paganism was integrated into the Roman church.
I reckon you're just trying to be brief here, but you haven't even considered evidence. You can't say there "isn't evidence" simply because you're unaware of it or fail to deal with it.
The same generations of Christians (AD 100 - 300) who believed in the ever-virginity of Mary are the ones who preserved, canonized and handed on the Scriptures you and I hold to be sacred. There's nothing in the Bible about which books are supposed to be Scripture; there's no Table of Contents; there's no signatures on the Gospels of Matthew, Mark, Luke and John: so as far as the text goes, they're anonymous. (How do you know who wrote them?) Nor is there evidence that the whole 27 books of the NT were "taught by any Apostle, nor believed by any Christian before 100 AD."
Except... EXCEPT that we know this from the history of the Church: it was the Fathers, the Synods, the Councils, the --- yes --- extra-Biblical writings and the Church authorities which "canonized" our sacred canon of Scripture.
You can't reject Apostolic Tradition without rejecting the canon of Scripture as well. It's really as simple as that.