i dont really get what you're trying to do ,
EDP doesnt even add exact 100% damage on level 1 ,
anyway , changing anything about buff / debuff mostly is on status.c
#ifdef RENEWAL_EDP
val2 = ((val1 + 1) / 2 + 2);
#else
val2 = val1 + 2;
#endif
val3 = 50 * (val1 + 1);
if you want to halven the EDP damage , just change the val3 value , or just add /2 in the end of the val3 formula