Well, the idea of the Berserker class is to strengthen weak servants by making them go insane. You didn't see Lancelot or Heracles making civil discussion. Why would Kariya or Illya do anything differently concerning ME?
Well, Kariya having a sane servant would be a major advantage to him, in reality, because his best chance of saving Sakura is to summon a servant who can kill Zouken or remove the worms from her somehow. I suspect that has a lot to do with why Zouken told him to use the Berserker class in the first place....
Actually, it's because really, Zouken gives no shits about Kariya, and probably would have just iced him and taken the seals if he came close to winning, to get that wish for himself.
Not giving a shit about Kariya would imply that he would just let Kariya do what he likes, though, it doesn't cause him to suggest summoning a Berserker. However, whilst it is unlikely, a sane servant could certainly possess something that could allow Kariya to kill Zouken and save Sakura, so Zouken is just safer if he avoid that possibility.
As a consequence, Sakura WOULD get to go free, but only because Zouken would be pimpin' out on his wish and not need her anymore.
Yeah, most likely. Assuming there was still a world left....
So if the Grail wasn't corrupted and Zouken wished for immortality would it rejuvenate his soul and make it stop rotting? Or would it freeze his soul in the state it was at the wish so he could be half rotted old man forever?
Probably the first, but it depends a bit on what exactly Zouken asks for as well.
