Well, it might be that he dumped you but still wants to see what you're up to. He could be having second thoughts deep down. Or perhaps he just enjoys seeing the snippets of your life without having to be directly involved. It's a bit of a mixed signal, really.
Yes, it's completely normal. Fanfic is a popular form of literature among many people, and your gf is no exception. It's just another way for her to engage with stories she loves.
She might want a story about a dream you had for your future when you were together. For example, if you once talked about living in a big house by the beach.
I'm not sure what exactly 'gf forces my mom' means. It could be that your girlfriend (gf) is putting some kind of pressure on your mom, but without more context, it's hard to say. Maybe she's trying to influence your mom's decisions regarding your relationship?
It could mean he's still curious about your life. Maybe he has some lingering feelings, but not enough to get back together. It's also possible he just likes to keep tabs on you out of habit.
It depends on how you feel. If seeing his name among your viewers makes you uncomfortable or it's preventing you from moving on, then yes, block him. But if you don't really care, you can just leave it as it is.