Translation:Except for you, we all know him.
The "for" should be optional in modern english. "Except for" and "except" are equivalent prepositions.
她 should be accepted as well as 他, right? They both sound the same spoken.
Yes, that's right. Since 他 can refer to anyone, it is more commonly used, even if it is clear 她 can be used as well.
"Except you" should be accepted, too. "Except you" and "except for you" are the same thing.