I get what you are saying about being 'way too forensic', but this is Game of Thrones we're talking about.
Also, it's actually come up just in the most recent episode - it was featured heavily in the book Sam finds Dragonstone locations in. Probably something to do with it being Valyrian Steel.
It's the dagger that someone tries to assassinate Bran with in the first series, which Littlefinger says belongs to Tyrion, but it actually is Littlefingers (or an associates, either way, LF is in possession of it currently).
Nah, she'll kill him with it, probably with Sansa's help. There's no point in putting regicide on him, because if Arya does somehow end up killing Cersei, she's not going to get away with it.
Not that she will kill Cersei anyway, Jaime's gonna be doing that. I don't think she's going to kill anyone else on her list, others will do it instead.
The problem for LF is that he isn't as in control as he believes he is. The reason he managed to always control Ned was because he was in King's Landing, his house where the Starks are out of their comfort zone. Now he's in the North, in Stark territory. The one card he has is the Knights of the Vale, which can very easily be taken from him if Sansa told anyone who LF kicked out the Moon Door.
Captain Pedantic here. Dragonstone is a place. Dragonglass (obsidian) is what they are looking for to make the weapons.


