Here's what I know so far:

I have about 15° of play in my steering wheel before steering action happens. The wheel is free to move within this but after the 15°, it encounters resistance and starts to steer.

I have checked the steering componentry while someone else is turning the wheel in this 15° window, and none of the components are moving. The pitman arm, the tie rod ends, the idler arm, nothing moves. Once you get past that window, however, they start to move.

I have tightened up the box multiple times from the cross-shaft adjustment screw, thinking that maybe it still wasn't tight enough. I finally got to the point where it was almost impossible to turn the wheel, so I backed it back off to a better position, but still there's play. Also, the play has been there since I bought the car.

There is no pump pressure to the box right now, but looking at the cross-section of the steering box, it looks like the pressure just makes it easier to steer (read: after the 15° window), not actually tighten the steering up.

I think it's time for a new box, but I wanted to get the opinions of others first. Thanks in advance!