Your mc is way out of character since he was like a humanitarian in his last life. He goes from helping people to letting his own citizens die if it's to keep the plot the same.
Go for the 2nd option which is right becoz as a demon lord aki should already know the procedure of a ascending demon lord or harvest festival it is a crucial moment ot rimuru to evolve so dont give rimuru a hope since if u do it he will somehow rely on u at most times, make rimuru independent