I've hammered off tons of flywheels in my day for impatience or lack of the right puller. the 504 is by FAR the most impossible - it's smaller and the case foes right up to the edge of it. it's a bitch.
I'd be pretty careful with heating the crank too just regarding the seal, it's easy to go a lil too hot with a torch, but it's also pretty easy not to, should work - im just sayin be conscious and careful.
yea, the best answer here is the proper puller, just buy one. it's worth it. bending the flywheel or melting seals or squashing the crank threads is not worth saving 15 bucks and 3 days.
if that is too mushroomed on the crank tip, grab the mushroom tip firmly and stroke
you can grind off the mushroomed partif you're careful to leave as much thread as possible, you've got some mm of threading before you're even touching the ones under load.