mate, just rip er off.. mate she'll be right.
get a crowie in there...
stuff i've done in the past:
hoist the engine box so it's vertical, box output shaft pointing to the ground, that way there is no load side load on the input shaft, and gravity lends a hand with the pulling part.. have a few people around to help wobble it off..
Otherwise a bunch of tires supporting engine and box and slowly pull/wobble off.
Is it even begun to seperate? ie, how wide is the 'crack' between the bellhousing and engine?
If there is no crack, have no fear to got nuts with a screwdriver.. there is usually a slow 'designed' for it somewhere.
If it's off more than a cm, and you can feel a 'spriggy' feeling,youve got your input shaft stuck a bit in the clutch..
just use force... as long as it's STRIAGHT force though!!!