Hmmm....
I think it's a little *too* dark. I think the part about Ryoga's head
was unneccesary. And the part about the baby having sharp teeth. I
think you could have a wonderfully dark story about two people, Akane
and Ranma, married too young, falling out of love, maybe with some
physical abuse by Ranma, and Akane finding comfort in another man's
arms. Let it be Ranma's baby - I think it would make the story more
poignant. In the real world, people don't get married at sixteen, and
when they do, it almost always ends badly. This story would be a great
way to show that.
So, lighten it up and make it darker at the same time, if you catch my
drift. I'd love to read what you come up with.