You don't need a crazy tool. Put the large adjustable wrench on the top locknut and turn CC while holding the handlebars. If you can't get it loose with a foot long wrench, you've got bigger problems.

Once the locknut is off, you can pull the keyed cable stop spacer out. Then any lockring wrench will work because it will be open on top so it no longer needs to be thin. Then take the knurled part off by hand.

You can assemble these headsets with some trial and error the same way, relying on the lockring, cup and keyed spacer to hold a position while the locknut is tightened down against them. That doesn't work very well with regular headsets, but the addition lockring makes it possible.