My thinking on #2 is pretty much in line with #5. If she was a virgin it is certainly pretty miraculous in the sense of being quite unexpected and very much involving God doing something. But this doesn’t have to mean magic or the violation of natural law. We know that pregnancy only requires fertilization not sex. As for how the sperm got where it needed to be then along with many of the other miracles, your guess is as good as mine. But I don’t think it even has to necessarily be a result of “messing around.” Call it happenstance or whatever but sometimes the strangest things happen by the most bizarre sequence of events.
Like jpm, I am neither convinced that Mary was a virgin nor am I opposed to the idea and the possibilities are many by which Mary could have been a virgin in a number of different senses of the word. Regardless, I do not consider this particular doctrine to define the Christian religion because it is not in the first agreement of Nicea 325 AD.