Ding Gu Xia! I am looking at a 2 weeks Spain route now

very close to yours:
fly in Barcelona, fly out Madrid.
Barcelona -> Granada (by night train) -> Seville (day trip to Cordoba) -> Madrid (day trips to Toledo, Salamanca)

Where did you buy your train pass? When/how did you reserve seats? Do the train station workers speak good English?

Thanks for all the details!