Iscool found a good reference here from ADIUTRICEM (On the Rosary), Encyclical of Pope Leo XIII...
“9. Since faith is the foundation, the source, of the gifts of God by which man is raised above the order of nature and is endowed with the dispositions requisite for life eternal, we are in justice bound to recognize the hidden influence of Mary in obtaining the gift of faith and its salutary cultivation - of Mary who brought the “author of faith”[6] into this world and who, because of her own great faith, was called “blessed.” “O Virgin most holy, none abounds in the knowledge of God except through thee; none, O Mother of God, attains salvation except through thee; none receives a gift from the throne of mercy except through thee.””
“”O Virgin most holy, none ... attains salvation except through thee; ...””
So it would seem that, yes, the belief is that you must go through Mary to be saved.
You have it exactly reversed - we don't go through Mary to be saved, Christ came to us through her. It's a one-way street.
Since you can't seem to find a source for the requirement that we pray to her, I suggest you retract that statement.
YUP,
That’s the damning belief of millions.
The quotations are from others and intended to show an intense reverence for Mary. As quotes, they reflect the speakers feelings. They are, I believe, intended to show her unique relationship with God only and not that Mary is the ‘gate keeper.’ Reading the full Adiutricem made this clear...at least to me.
Ultimately, the Nicene Creed is the statement of Catholic beliefs.