it was kishimoto's idea to have shikamaru feel the impact of naruto's punch on gaara, so its not really the animators' fault for that. What could've happened was with kin he might have released the shadow just before she hit her head (which could also explain why he needed the shuriken as a distraction. That way when he releases the jutsu at the last moment, she wont even realize it and will still attempt to dodje the shuriken the same way shikamaru did). As for the 8 sound nins, shikamaru knew that there was a 9th hiding somewhere, so he threw the kunais with the intention of them being deflected. He just wanted to see where the 9th one was hiding