the design process is not yours . you are trying error. have you consider how RC affect the psr,the trans response,the stbility of bandgap? the critical value of RC for above terms? this is not a easy work, but you just try little condition to make conlution !
suggest u change architecture of bandgap. using kuijk cell. do your company have some reference circuit for you ? the 3sigma of this structure of bandgap is so big . it will out of your control ! and what about your triming method ?