I thought minors in Judea in the 1st century AD did not make decisions; they did not live in 21st century America, where teens rule. I believe their marriages were arranged by their parents, or guardians (given that women really could not earn their living in those days).
I never paid much attention to the actual bethrodal issue of BEV Mary, but I believe the context in which it is revealed in the NT is that she "was bethroded" and not that she "bethroded herself" to +Joseph.
I think you're exactly right about this. However, that would put Mary in even more of a jam. :) If she never had any intention on having conjugal relations with a man, then she would be guilty of dishonoring her parents. "Wifely" speaking, she would be damaged goods, and would have been honor bound to inform her parents that she was not suitable to be given away in marriage.
I believe that your Tradition says that Joseph was a much older man (I have no opinion). If so, I doubt he would be interested in marrying any 16-year-old mostly for her sparkling conversation. Had the angel never appeared to Joseph, which Mary could not possibly have known would happen, then I think Joseph would have rightly felt ripped off. :)