Well...it's not a solution to your problem but it could help...you have to start your game again or load an old savegame.
At a certain point of the game Jessica (your mother) will ask you to follow her to search some secret rooms into the Palace, you
don't have to find the "Communication room"
In this way you'll be able to harvest
all the spice from a limitated number of sietches on Dune, Harkonnen won't attack your north territories and you won't loose troops and equipment. Yeah, the story of the game won't go ahead but you'll earn lot of spice...and the Emperor
can't ask you spice.
After 60-80 days you'll finish spice and you'll be ready to find the secret room and start the game with a good background
k:
(Remember, Harkonnen won't attack territories with no more spice)