Well, as of now, there are several Umbrella Academy comics by Gerard Way. The series has been ongoing and evolving over time. But to get the precise number, it's best to refer to comic book databases or the publisher's announcements.
Umbrella Academy is indeed based on Gerard Way's comic. The comic provided the foundation for the show's world-building, character development, and overall narrative. However, some minor changes and additions might be made to make it suitable for the TV format.
Definitely not. Twilight is centered around Bella, Edward, and Jacob in a world of vampires and werewolves. It was created by Meyer with her own unique ideas. Gerard Way is associated with a different kind of music - related and comic - related work, and there's no connection between Twilight and his fanfiction.
No. Twilight was an original story created by Stephenie Meyer. It has its own unique plot, characters, and world - building that are distinct from Gerard Way's works.
No. The inspiration for Twilight came from Stephenie Meyer's own dreams and her interest in the vampire genre. There's no evidence to suggest that Gerard Way had any influence on it.