Got it. Sorry for the goofy questions.
If I can add to what @mlucas and @Lakis have already said, I think you get the idea that a traditional "main character" and a Dramatica Main Character are two different things, one clearly defined and the other much less so, sometimes seemingly interchangeable but oftentimes not. That said, I think the Dramatica term most appropriate for how you are using "main character" would be "player".
The concept of “player” is found throughout Dramatica and differs from what we mean by “character.” Dramatica defines a character as a set of dramatic functions that must be portrayed in order to make the complete argument of a story. Several functions may be grouped together and assigned to a person, place, or thing who will represent them in the story. The group of functions defines the nature of the character. The personage representing the functions is a player.
If you are looking at Frodo's story, all events being exactly the same only seen from another perspective, then I agree that he seems to be fulfilling a protagonist role, or embodying the Pursuit characteristic at the very least, but could also potentially have other roles, such as the IC, depending on how this hypothetical version plays out and where it's focused.
Similarly I don't think the audience having a POV on a character is the same as the Storymind's perspective on or within the story. However, i have a hard time imagining what a personal perspective would look like without being able to follow that characters POV. So...perhaps not?
Dramatica theory suggests you not put two separate protagonists in the same scene, so yes, you would have one of them maintain the Protagonist characteristics while the other let go of them for that scene. The exception would be if you had multiple characters that were meant to represent a single Protagonist role. An example of something like this might bethe Salamanca cousins on Breaking Bad (not that they are a collective Protagonist, but that they are a collective of whatever their story role is...Contagonist, maybe?).