Now I'm confused. Are you saying that you have a level 38 game with completed storyline that doesn't offer you jobs on Crete, but you change the level to 5 and it does? That makes no sense at all. Would you mind sending me that file?
As for progress, I mean where you are in the story. For a single player game, the player's difficulty level is based on the values in rankdiff, which is determined from the MissionNum value in the savegame. That's why FL Hack's "Higher paying jobs" worked, because it uses the multiplayer code. It's also why you shouldn't mix savegames from the two content.dll versions, because the numbers changed (1.0 is completely sequential, but 1.1 skips 6, going from 5 to 7). Since Freelancer tests for a specific number, you'll never be able to advance level.