You can start by looking on fanfiction websites like Archive of Our Own (AO3). There are a large number of fanfiction pieces there, and you can search specifically for female Miles Morales fanfiction using the search bar. Just type in 'female Miles Morales' and you'll get a list of relevant stories.
It varies depending on the specific comic or media adaptation. But generally, it can span a significant amount of time with various plotlines and developments.
The number of Miles Morales comics varies. Different publishers and series contribute to the count. As of now, there could be around 20 or more depending on how you define and count them.
In most comic runs, Miles Morales is in his early to mid-teens. His age can fluctuate a bit based on the creative direction of the writers and the chronology of the storylines. But generally, he's considered a young adolescent with a lot of growing and heroics ahead of him.
The length of Miles Morales' story can vary depending on the specific comic or media it appears in. But typically, it's quite extensive and full of exciting developments.
You can start by checking out reviews on comic book websites. Sites like Comic Book Resources or IGN often review graphic novels. They'll give you an idea of which Miles Morales ones are highly rated.