Correct, but the Blessed Virgin Mary was in this state PRIOR to the Conception of Christ.
Colossians refers to believers (not just Mary) as possessing God's "fullness" quite a few times. When a person is saved (as Mary realized she was in the Luke passage) he/she has come into God's fullness.
Yes, Mary already knew that she was saved. This was BEFORE our Lord offered salvation to the rest of mankind. The Blessed Mother didn't know that she would be saved, she knew that she already was.
As far as your ark discussion, that is allegory and is a nice picture but I don't see anything close to such a comparison in the Scriture for Mary.
Really, you don't think that Jesus Christ offered a new Covenant?
As were the Old Testament saints. Faith was granted before the historical advent of Christ. Abraham also experienced salvation so was "full of grace".
Really, you don't think that Jesus Christ offered a new Covenant?
If one believes in a New Covenant it's certainly not a prerequisite that one must believe the allegory that Mary is a parallel to the ark.
Abraham also knew he was saved prior to Christ's salvation being offered to the rest of mankind, God declared him "righteous". The entire OT points directly to salvation through a Savior and Jewish followers who had faith in this promise were also "full of grace". Mary knew she needed a savior and she knew Jesus was her savior. Had she been "sinless", where was a savior needed?