I agree that this is a very complete discussion of who/whom. I would encourage you to take this hard work and conceptual knowledge and apply it as generally as possible. In this case, any rule related to who/whom can also be applied to all other subject/object pronoun questions:
-use object pronouns (her, him, me, you, us, them, whom) when the action is being done TO that person:
Bill gave the ring to HER.
Bill sent HIM a letter.
Bill told HIM about HER.
-use subject pronouns (I, you, he, she, we, they who) when the action is being done BY that person.
HE gave the ring to her.
WE told you it wouldn't work.
I went to the store.
Notice how subject pronouns are paired with a verb (He gave, we told, I went) but object pronouns don't.
Brett Beach-Kimball | Manhattan GMAT Instructor
Manhattan GMAT Discount | Manhattan GMAT Reviews