He might be really intrigued. Naruto is always open to new ideas and adventures. Seeing different versions of his world and himself in the multiverse fanfiction could make him excited to explore those possibilities, even if they are just fictional concepts.
Well, it really comes down to a few things. Do you have common interests? Do they seem like a genuine and nice person? If the answers are yes, it might be a good idea to friend them.
Well, it might indicate that they want to know more about your life or are at least curious. Maybe it's a sign that they have some level of interest in you.
When your ex watches your stories, it could indicate that they haven't fully moved on and still have some lingering feelings. However, it could also be a casual act without any deep meaning. It really depends on the context and your history with the person.
Maybe it doesn't mean much. They might have been scrolling through and stopped on yours without any specific intention. Or it could indicate they're curious about how you're doing after the breakup.
He might be really surprised. In alternate universe fanfiction, things could be so different from his own world. For example, he could see versions of himself with different powers or relationships. It would be like looking into a strange mirror that shows a distorted but fascinating view of his life.