40 peroxide will bleach black hair blonde, but according to the jerry g method you have to bleach twice which, given your very SHORT timeline is just not feasible. bleaching your hair twice (no matter what strength peroxide you use) will GUARANTEE that your hair falls out... bleaching just once and then re-dying your hair will GUARANTEE that your hair falls out (you need to wait an absolute minimum of 1 week between any kind of hair treatments - the pros recommend a min. of 2).

the way i see it your only other alternative is to shave your head. bald.