Nitro 4.0L Damper-pulley

Been working for a couple of days trying to remove the damper/pulley on a 4.0L Nitro. Fought the wrong tool for a day. Wound up renting one from Autozone. The tool at least stays on. I cannot budge the thing with a half inch breaker bar on the 27mm socket. Anyone have suggestions?
The tool says that it should not be used with an impact wrench but I am getting increasingly tempted.
Thanks,
Craig