As soon as you feel any play, it's too late. The BB axle is much harder than the cranks. To work it loose like that you will deform the square taper. It needs to be pulled straight off the axle.
Best to do it properly, some LBS will have a tools that designed to rethread the thread bigger to allow a bigger crank extractor to fit, I've done that on a dozen of bicycles before.
Do. Not. Fucking. Do. That!
@JWestland don't do it! don't!