Could you tell me the case of relative pronouns in the following sentences?

I am trying to figure out the case of relative pronouns in the following sentences. Could you please tell me whether they are used in nominative case or objective case?

1. What I have written, I have written.
2. All that I said had no effect on him.
3. He was the most eloquent speaker that I ever heard.

4. Who am I that I should object?
5. Who that saw her did not pity her?
6. What is there that I do not know?

Thanks,
Richards.