We can do the horn after the brake lights if you wish....then down the list. One step at a time.
I don't know what the blue thing or the silver thing is. Maybe an inline fuse but doesn't seem so, maybe fusible link. But a fusible like is poor selection for those wires and would not be original. I'm thinking just connectors/crimp splice. Don't know. If no fuse inside, not a fuse holder. A fusible link is just a piece of "special" wire but not usually spliced in the middle of nowhere.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn