Second, others in the Bible are also called "favored" or "highly favored" of God, too. It doesn't imply anything more than one on whom God has shown his favor. It doesn't mean they aren't sinners or any less sinful.
Only Catholics believe that the woman in Revelation 12 is Mary. There are counter (and better argued) arguments that the woman represents Israel (as Protestants have long agreed). There is nothing in Revleation 12 that argues the woman is supposed to be Mary, this is just how Catholics choose to interpret it.
On Luke 1:28, you rely on obfuscatory Protestant translations, designed to propagate mariophobic falsehoods.
The original says “Kecharitomeneh”, a unique to Luke word formation from “charis”, “grace”. It is true that “charis” is sometimes translated “favor”, but never in theological context. The same Protestant translations that have “favored” in Luke 1:28 always translate “charis” as “grace” everywhere else. It is simply a dishonest attempt to trivialize the manner of the angel’s salutation, even though St. Luke makes a special effort to underscore its uniqueness in the following verse.
Further, “kecharitomeneh” is past tense, — something English translation cannot properly convey. This points to the fact that Mary is not filled with grace at the time of the Annunciation, but that she had been filled with it all along, hence Immaculate Conception.
St. Stephen is also described as “full of grace”, but the context is clear that he experiences a surge of grace and fortitude as he speaks, and the origional uses a different verbiage.
The woman in Apocalypse (Revelation of St. John) is described as mother of Christ (Apoc. 12:5, 10). The interpretation that she is somehow Israel is just plain silly.