Reading manga for free from unauthorized sources is not recommended. But some legal platforms like Comixology or Kindle Unlimited might have it available for a subscription fee. Also, sometimes libraries have digital collections you can access with your library card.
Yes, it's possible that Maximum Ride could read fanfiction. Just like many fans of a series, the character within the story, if in a more meta - situation, might be interested in reading the creative interpretations that fans have written about their own adventures.
I don't have the exact number off the top of my head. But a quick search on manga forums or asking fellow manga enthusiasts might help you get the answer you're looking for.
Well, as far as I know, the Maximum Ride manga consists of approximately 8 to 12 volumes. But the exact number might vary depending on different editions and releases.