I can't see any brakes holding anywhere near 400nm+ of torque. I did mine on the engine stand with the flywheel locked.
Look at the size of torque wrenches we are using to achieve that torque and go figure.
I personally can't see how an interference fit between the balancer and shaft would help, the clamping force comes from the bolt and areas that it compresses, the woodruff keys are there just to align timing marks for the cam pulley and balancer at TDC.