1. Would "Who are they asking? or Whom are they asking?" be correct?-- The first is informally acceptable; the second is formally correct.
2. It is he who wants to read the book. And where can I find rules?-- The 'rules' are broken all the time. The dependent clause should determine the case ('he who wants'-- 'He' and 'who' are subjects)-- plus the copular 'be' gen