The primary issue comes down to how κεχαριτωμένη is understood.
The NASB translates it as favored one. (As a side note so does Wallace in Greek Grammar Beyond the Basics). Also, the NASB is the closest literal translation we have available outside of an interlinear.
The interliner translates it as [you]favored with grace.
The majority of the translations render it this way. Douay-Rheims renders it full of grace as does the Aramaic Bible in Plain English.
The Expositor's Greek Testament notes the vulgate translation is incorrect and translates it as much graced or favored by God.
The Cambridge Bible for Schools and Colleges translates it as having been graced by God.
Pulpit Commentary also noted it should be rendered as "having been much graced by God".
Vincents Word Studies also notes it should be translated as thou that art highly favored.
These commentaries note the Vulgate translation is incorrect. As we both know DR is based on the Vulgate.
Another thing to keep in mind, the KJV translation is not based on the oldest Greek manuscripts available. It's a good translation, but isn't based on the best texts available.
The issue comes down to is this a title or a greeting.
The κεχαριτωμένη is a perfect participle, middle/passive voice, vocative female singular. Being middle/passive indicates the subject is being acted upon.
I think we all agree Mary is being graced by God in that she has been chosen to be the mother of Christ. The vocative indicates this is the voice of direct address so there is no mistake who Gabriel is talking to. We do not know who else is home....but he's talking to her.
Is she being set apart from other women? Most assuredly.
However, none of this indicates a title or a sinless nature being conveyed upon Mary.
Again, the catholic encyclopedia online article of the immaculate conception concurs there is no direct biblical support for this position.
2) I would hope that in your studies you have heard of "Archetypes", Foreshadowing in the OT directly pointing to items in the NT. Adam, Noah, Moses, David, etc... were human Archetypes of Christ. The Ten Commandments, Manna, and Aaron's staff were all inanimate Archetypes.
A careful open minded study of the OT will also see Human Archetypes of Mary, these include; Ruth, Ester, Judith, and Bathsheba. They will also see two inanimate archetypes. The first is Noah's Ark, and the second is the Ark of the Covenant.
The thing with Archetypes is that they are all lessor foreshadows of their fulfillment. The description of the materials and construction of the man made Ark of the Covenant is a pale imitation of the perfection achieved by God in Mary, and this is confirmed in Revelation chapters 11/12.