If by the latest chapters you mean 315, I have read it. Kakashi explicitly states that he can't match Naruto in KB because of the chakra consumption. He never mentions that the technique requires insane skill to learn. Additionaly despite the fact that it is origonally refered to as Kinjutsu (Forbidden Jutsu) almost every ninja above genin level appears to know about it. Many can do it. Additionaly it is explicitly stated in the chunin exam finals that KB is a Jounin level jutsu because it consumes a lot of chakra.
Every ninja above genin level? Are you so certain about this fact? I would check my facts first before rushing to post.
No.... Sakura learned tree walking after seeing it once. Naruto spent a lot of time at the pool. Then Jiraiya showed up. Then he spent more time on the lake. True his chakra was messed up, however even taking that into account it took him a lot longer then it took Sakura to master tree walking.
You seem to conveniently forget that Naruto had a seal on him that made chakra control impossible. Try taking Sakura's chakra control and see what you get. When the seal was lifted he managed to walk on water in an instant.