Hello I will help you with your question,
There is a special tool to hold the pulley while you loosen and tighten the bolt but it is $250 so maybe another way can be used. If you hold the flywheel the crankbolt can be loosened but be careful you don't want to chip a tooth on the gear.
Remove the starter and wedge the ring gear then loosen the crank bolt, the pulley can be walked off the crank with two screwdrivers once the bolt is removed
Let me know what I can do to help
An impact would be nice but do you have air available and can you get the impact to the head of the bolt?