Lookin for help here.

I have a '91 Toyota 4x4 PU. I had one of the right front brake caliper pistons sieze up, and I now need to replace the caliper and rotor. I have the front end disassembled to this point:

Wheel and caliper is removed.

Front locking hub is removed (cone washers were a booger!).

I'm at the point of removing the hub from the axle, and I want to grease the wheel bearings while I'm in there. I'm now looking at what appears to be about a 54mm nut, with some sort of clip or locking mechanism behind it that is keeping it from rotating. How do I get this nut removed?

Another question. This truck has almost 200,000 miles on it. I notice that the front axle stub (the splined part that extends through the hub and engages the Aisin locker, has about a 1/16" degree of up and down and side to side play in it with the locker removed. Is this normal? Is there a bushing or bearing that needs to be replaced? I didn't notice any play when the Aisin locker was still bolted on.