Marrow, some issues.

There's essentially no way your character could be born a few years into the Reign of Sai and be fifteen. The official Reign of Sai only lasted fifteen years.

Secondly, if you're not being taught the sixty-four strikes, you won't know it. It was basically a Hiden passed down within the main Hyuga branch that Neji only succeeded in mastering because he's a plot-induced badass.

Lastly, there was no 'assassination' attempt on Sai. It was a drawn out, full-scale war inside Amegakure that lead to the destruction of an entire city that was basically a bastion.