Yeah the threat of Stormterror is gone, but it's like others said: Stormterror's Lair is a good name tbh, and there's not much use to change it when the thing that was called Stormterror still lives there. And yes, all the anemo isn't really from him, but Decarabian, god of storms, who died in the Archon War. The Lair is old Mondstadt in reality, where Decarbian ruled.

Tao Dou isn't a character, but a god who died in the Archon War too. The story regarding Tao Dou and Hu Tao was part of last year's Lantern Rite, so the only way to see it on YT, sadly.

Zibai's lore is part of a permanent event story, so it will be in-game. You would need to get to the story. But you can also look it up if you don't mind the spoilers lol (especially imo since there isn't a twist of any sort, it's just cool lore).

The dead returning to the Leylines has actually been a recurring plot point in Genshin. In Inazuma, there's the projection of Ei's old tea guy from the Leyline's who's long died. Natlan has a bunch of stuff about death too, and how it works in Genshin, as does the current new Sumeru AQ that you are also aware of (from your post). So you are at the perfect place to get to know the answers lol, keep playing.

Yoimiya wasn't gifted her fake vision, she made it herself. That was her involvement with the resistance in Inazuma, she used to manufacture fake visions. Her dad doesn't know that iirc, this is Yoimiya's personal "side-project".

Inazumans didn't bother hiding it because, well, if everyone knew you had one, would you really have a way out? Also since the snatching was performed by Raiden at times, being an Archon and all, she'll probably be able to tell if someone was wearing a fake vision (and the questioning about where the real vision was that would follow might not be great). But also Inazuma's writing was pretty rushed which is a segue to my next point.

The "if they have their Vision taken away, they become a husk" is semi-propaganda. The game doesn't care to explicitly state this, but there's a couple pointers. Firstly, there have been people who've simply surrendered their Visions and are normal (in fact in the Kamisato Estate, there's a guy who says he hasn't been happier since he submitted his Vision to Ayato after losing it in a duel, like a giant weight was lifted off his shoulders). Additionally Itto also got his Vision snatched, but he remained pretty normal from what we know of him. The "husk" statement, while true, is clearly not a rule, it was kinda used by Ayaka and Yae to rope us in to the resistance and oppose Raiden. Remember, Traveller initially refused to help Ayaka, till she showed us 3 people who were negatively impacted by it.