I just love the response times on the forum. 1 hour, problem to solution. That basin wrench is a good call. The shaft on those wrenches isn't 18" long to get above the skimmer but if you still can't get enough torque you can use a piece of PVC pipe, cut a couple slots in one end to fit over the wrench handle, then a channel-lock plier to turn the pipe from above. Make an extension.
Al