If Mary was free from original sin then her parents and their parents etc... must be also.
It does not follow. Mary herself was not god, she carried God and this, the speculation goes, necessitated her purity as the tabernacle of the Word. St. Anna did not carry but another human.
I would agree this is a bit speculative. The scripture merely says "Hail full of grace". The Greek there is past tense, and it is a unique Greek word not used by Luke anywhere else. This leads us to think that hte filling of grace occurred at some point before the Angle spoke. The natural point of time for that is conception. But one who goes by the scripture alone is not obligated to reacht he same conclusion Catholics reach.
Mary would God be powerless to chose another female?
We believe that God foreknows all events, so He foreknew Mary's consent also. It is pointless to speculate if another woman would have been chosen, since we don't have multiple universes and in this one, Mary was chosen.
Why did it take 1900 years to establish the dogma?
The Catholic dogmas are not established by council. They are proclaimed as being the belief of the Church since day one. The Pope chose to proclaim the marian beliefs in question as dogmatic because the world was falling into a number of inhumane heresies, atheistic darwinism chief among them. At that point it became important to stress that human existence has a supernatural dimension and has heaven as its both source and destiny. But the Pope would not have been able to proclaim the dogma if the beleif had not been present in an inarticulated form in the Church.
If Mary ascended where is the empirical evidence at
That is sort of the point: there is no known relic of Virgin Mary when there is a relic of virtually every saint of the early Church period.
Utter nonsense. Many theologians (Ireneus, Jerome, Augustine, Ambrose, Epiphanius etc...) were skeptical and not exactly sure. "Consensus" was not reached until "1900" years later, "1500" if you count from 'De Obitu S. Dominae', how convenient.
I will take the Bible plus early Church Father "questioning of the whole deal" (Some had a belief but not enough to to rise to the level an "dogma", remember that) over Gregory of Tours, De Obitu S. Dominae, hearsay and Pope Pius XII any day.