These things are a beeatch to remove.
I cannot imagine the manual would imply that compression or anything else would counteract this sort of torque.
Is the pan off? You can sometimes position a piece of wood between the crank and the block.
Assuming you can get the engine to stay still;
The best way to generate the torque required is to position the breaker bar handle such that you can lift it off the floor with the saddle of a hydaulic floor jack. Unstoppable, safe, and requires less clearance than various 'lever arm extensions'.
Best of luck.
1986 300E 5-Speed 240k mi.