Other than the putting it near a wall bit that's exactly what I've been doing. Plus hosed the fucker down with some spray lube stuff and let it soak. It's not budging.
I always succeed with a vice. Everything in my world is better when there's a large solid lump of steel to hit things against :)
I've been able to remove freewheels by:
I think the sharper impacts of the hammer actually releases the freewheel quicker than the vice/busdriver method.