I'll point out that the wear on a badly worn cross feed screw is usually in the middle 1/3 of the screw. If you install an adjust nut and tighten it up in the badly worn area, the screw will lock up when you try to go out of the worn area. How much backlash (use the dial reading to specify) do you have? Is it substantially the same in the high usage area as with the cross slide almost fully retracted? If it isn't, you are going to have the above problem. If it is and it truly is excessive and not just more than zero, the probable culprit is feed screw end float, which should be adjustable to near zero.