well for one, two species that different cannot mate. Just throwing it out there.
The broken master sword idea had been done in other fanfics(mine for sure.)
Like stated before, major plot holes. And instead of you going to the castle to get the sword piece from ganondorf, have a ancient monster from underneath castle town be attacking the castles surrounding area. And i still just dont really like the fact that two different species could have a baby together. Like even in the most desperate of times, that would never happen. So idk.

Edit: I give it a 3 or 4/10.