get new scroll from CT NPC. (3 inks)
go to NS copy your weapon stats to the new scroll.
go to CT again the goblin NPC to remove the materia that you dont want from the new scroll (point by point!). so if you want to remove all the 17ACC. you have to remove 1 by 1.
then you can infuse CRIT/DET (using 17 alex and might/aim materias IVs?) in the empty available slots in the new scroll. once its 75/75.
go to NS and apply it to your weapon.