Many Questions about negative and indefinite words

Many Questions about negative and indefinite words
 

Hola - I'm using the Ultimate Spanish CDs at the moment for review and practice. They're quite good. In one section however, I have many questions (as I have had on this topic before).

I'm supposed to answer each question in the negative. Answers are provided.

1. Q: Fuiste alguna vez a la Isla de Pascua? A:No, no fui nunca.

The answer makes perfect sense and seems the only logical choice but I'm not sure how to translate the question - Have you ever been too Easter Island?? How about: Fuiste a la Isla de Pascua? or Fuiste una vez a al Isla de Pascua? I'm getting hung up on the "ever" part in English. In Italiano: Sei stato mai a la Isola di Pasqua?

2. Q: Va Isabel a tomar algebra otra vez? A: No, no va a tomar algebra nunca mas.

The question would be: Is Isabel going to take algebra again? Nunca mas in the answer feels like - Never more will she take algebra. Could I just reply: No, no va a tomar algebra otra vez (no, she won't take it again)?

3. Q: Algunos jefes renunciaron al puesto? A: No, ninguno (ningun jefe) renuncio al puesto.

confused about the question - Have some of the bosses resigned their post? A few of the bosses...? Have any of the bosses...? Could I have said: Unos jefes ren....? Could the answer have been: No, nadie renun...

4. Q: Conocio Osvaldo a alguien por fin? A: No, no conocio a nadie.

Could the answer have been: No, no conocio a ninguno. ?

5. Q: Quedan algunos duraznos? A: No, no queda ninguno

Why can't the answer be: No, no quedan ningunos. ? Does it always stay singular in the negative reply? Is it the difference between: There are not any left. and There isn't one left?

6. Q: Siempre limpias la casa los sabados? A: No, nunca limpio la casa los sabados.

Ok, that sounds good. What if I had wanted to say: Do you still clean the house on Saturdays? No, not any more. How does this sound:
Todavia limpias la casa los saboados? No, nunca mas. ?

7: Q: Has visto a alguna de las empleadas? No, no he visto a ninguna

could the question have been: Has visto a una de las empleadas. ? and could the answer have been: No, no he visto a nadie. ? Is that the difference between: No, I haven't seen any of them. and no, I have seen no one?

It could be that multiple choices are all correct but I'm just exploring the nuances and trying to get a feel for when I really sound non-native.

Thanks for all the advice.

Chris