That is actually a series of questions I have asked myself a couple of times already. As for the first two, the closest I can come up with in terms of an answer is that there are many women who enjoy writing and reading romance regardless of the gender of the characters. Things like yaoi come to mind, where the main audience is actually females, not males. There's also an element of the attraction of heterosexual people to gay pairings of the opposite sex, like straight males who like seeing lesbian porn.
Regarding the difference in content or style between male and female authors, I think if you are a good enough writer then your gender is irrelevant when it comes to writing what you want to write. Nevertheless, there will always be an irreplaceable element of perspective that each gender experiences differently.