Firstly, where do you get "Sakura can barely do anything with them" from? Secondly it's still Sakura, because Shinji can't do anything without Sakura's help, whereas Sakura has at least some level of potential.
She was still playing with him, though. In a different way (because Shinji wouldn't let her do what Lancer did), but she was.Except she punched him out of a window. Lancer had fun by seeing how long he could hold out.
Shinji Rider can't, no, and probably nor could Sakura Rider. But, she'd make damn sure that she didn't have to....Still means she can't beat her in melee on even ground.
Of course not, but why the hell would Sakura wish for immortality for Zouken? The guy has tortured her for eleven years. Even Sakura hates him (and that's saying something...). Why not just wish to be free of his control instead?Sakura didn't even want to fight in the War. She doesn't have a wish, except maybe "I wanna be with sempai", and that wouldn't exactly take much mana out of the infinite wishing machine.
Plus, Zouken couldn't remove the worms even if he wanted to. So, if she didn't wish for freedom, there's a danger of him retaking control of her in the future, and she certainly wouldn't want to bring Shirou into that. Plus, I doubt Shirou would be willing to just let him live (with immortality, at that...) after all that he'd done, and freeing Sakura from his control would risk his situation being exposed to either Shirou or, worse (for him), Rin (and, by proxy, the Association, who would probably be very interested in using him for "research").
Erm, what? Since when does intelligence have anything to do with ruling a kingdom? And, yes, Saber's lack of intelligence (or, rather, her "honour before reason" attitude to things) did lead to the downfall of her kingdom, because she did things that were always going to incite rebellion. Plus, she's not exactly renowned for her tactical prowess. Her method of fighting is "charge at the enemy and slash it until it falls over".
As for Medusa, she was a fucking monster most of the the time. Monster forms tend not to have much intelligence, regardless of how smart the original is....