My saves are around 440KBThat is probably because your save file grew too large. Can you attach it here?
You should not load a save and save immediately after, but let some in-game time pass (sleep some nights, do quests, talk to people). When you exit the game, an auto-save will be created which might just exceed memory in that case.
Note that the original unmodded game has the same issue, but not to that extend (saves will also grow but you have more space -- the mod needs some more space after all).
The "persistent" file is 11,787KB