Some information that i know :
i) Pilot require good result on English, Physics, Mathematics (Add Math not sure either it is in the consideration of the airlines). But since you are going to sit for SPM, so please try to concentrate on all subject if possible. Since you will need to have a backup plan in case there are obstacles in becoming pilot such as taking diploma etc.
ii) rough estimation would be around RM200k-RM250k. You need to check with the flying school to confirm.
iii) One alternative is the have loan, but be mind of the interest rate. You borrow RM250K but you ended up paying the total of around RM500k for 10 years loan
One suggestion is that try to wait for the cadet pilot from the airlines. They normally open the intake once a year. The competition is quite tough but still it is worth to try.
Hope this helps