I would try removing your freewheel by clamping the tool in a bench vise and then place the freewheel on top of the tool and turn the whole wheel to loosen it. You don't have a lot of room to work with but because it is a splined tool you might get lucky. Or you could clamp your adjustable wrench in your vise with the splined tool in it and again use the wheel for leverage.

Good Luck

vjp