And the kunai thing, remember that Orochimaru himself stated that Tayuya has a bad behaviour and gets caught up in the game easily, so she though that Shikamaru was trapped inside her genjutsu, right?
So, inside the genjutsu, Shikamaru throws the kunai and "misses" _because_ of the genjutsu, or so Tayuya thinks. "Because" of the genjutsu, Shikamaru releases the Shadow-Bind and allows Tayuya to get closer, and Tayuya surely thought something like "Oh look, the kunai which he threw at me and missed! Wouldn't it be ironic if I picked it up and killed him with his own, last, useless weapon? Yes, it would!"