Here, Ditto transforms into Persian and then proceeds to crit repeatedly (presumably taking Persian's base speed, but you can check that) with Ditto's attack, which is incorrect according to this post and Crystal's post further down.
Yes for critical hit calculation: Persian's non-modified attack, defense and special, but Ditto's base speed for the CH ratio. Other stuff to do with transform is alright I think. It correctly copies the current stats of the target at the time of transformation.