bleach, bleach and more.... bleach.
the mold may have gotten up into the back padding of the rear seat, the rear seat bottom cushion and the carpet, and floor liner of the car.
the spare tire area, and the other side (i think it has a little storage nook; those all are suspect for mold, and the nice linings of carpeting is probably moldy too.
DONT use any stuff that says, scent, pine fresh, odor, or other 'neutralizing' stuff (like febreeze etc.) those only mask the problem. you need bleach to KILL the mold. then in all likelyhood you should have the interior pressure washed, but that would cost more than the car is worth. (stripping all the interior out, washing, and reinstalling.)
agree that bleach is corrosive, but between mold and bleach i'll take bleach any bay. if it gets rid of mold it must be good.