guess i'm not really in a position to advise you..tho based on things i read in diff forums and CX's website, I can assure u they do take on shortsighted ppl as long as it can b corrected (not quite sure if +600 is alrite for them tho, I'm sure some other will be able to advise u on that soon).
With regards to what subject u shud study, physics and maths is definitely a plus as flying a plane requires a fair bit of knowledge in flight mechanics and aerodynamics. Having said that, what pilots know abt flight mechanics and aerodynamics is only superficial, nothing involves complicated maths like partial differential equations or Navier Stokes equation.
N son, if u do get an interview, dun ever tell them u actually want to be a pharmacist...
Ur english... well u're not the worst however i think u do need to brush it up a bit (u need to pass an english listening, as well as a grammar test in the first stage of the selection process)...afterall u dun wanna sound like a Hongkie during the interview...mind u, some local pilots do speak english in an awful HK accent... as long as u can communicate with ur colleague n ATC then it's fine i suppose...
So make sure this is what you wanna do and just fill in the application form in ur own handwriting (which is a pain in the **** btw) and send it off.