#1 - you are suggesting that Gai is slower than lee - and by that somehow implying that lee > gai?

#2 - the chakras are mixing - Naruto is able to extract chakra from kyubi and some of kyubi's chakra is being used as Naruto matures as a ninja - its not necessarily Kyubi's soul takes over Naruto's althought hat is quite possible. But as jirayia says in oh say episodes 54 or so (when he is training Naruto on water walking and unseals orochimaru's seal, the seal is meant to allow only chakra to leak out.

and as far as seeing fast lee/gai - if you remember Kakashi could see Lee moving with his sharingan in episodes 48-49 when lee had his weights off + 5 gates opened... and he has ghetto sharingan so we can safefully assume that Itachi coudl read it like a freaking open book...also note

Sasuke's undeveloped sharingan was able to read Gaara's movement when he was using his tail to fling himself at sasuke - sharingan predicts movement (i.e. kind of see future - refer to the episode with Zabuza + kakashi fight - episode 18 it hink).

The shin otaku version left a whole damn lot unexplained with their translations - for example the scene where Kakashi is fighting Itachi before he whips out the mange sharingan - the translation doens't make any sense - and the Naruto series is actually quite good at explaining what happened in certain jutsu battles

as far as Episode 83 is concerned - i would expect alot to be filler but there is relevance if memory serves right so dont be too disappointed