Modifying amount of thieving skill points per level on a given thief

Is there a way to do that? I am multiclassing with EE Keeper a F/M/Shadowdancer and i already corrected the backstab progression in the .2da file but i cannot find a way to decrease the amount of skill points he gains per level from 25 to 20 as it should be with a SD. Anyone knows how to do that?