Why wasn't a Uchiha asked to control the Nine Tails during its attack? Madara or Tobi had controlled the Nine Tails to attack Konoha during Naruto's birth. But there were other Uchihas in the village such as Itachi's father. So, the village could have made use of them to defend the Nine Tails by controlling it using their sharingan. Why didn't they do that?

Another question: Why were the three sannin not seen during the Nine Tails attack?
As for the Uchiha, the nine tails was already being controlled by Tobi at the time, so I doubt anyone would be able to control him on top of that. 

Not to mention, the Uchiha weren't exactly trusted at the time, following the Second Hokage's rule. 

As for the three sannin, it wasn't explained anywhere, but it isn't hard to imagine them being at a remote mission and out of the village.