Couple shifting problems..

If the thrust bearing is worn so much that the crank walks back and forth you're going to have bigger problems than clutch adjustment issues. The thrust bearing endplay is mere thousands of an inch, you should not be able to move the crank back and forth by hand.

As mentioned above the throwout bearing could be going bad, or something in the clutch linkage could be slowly bending and about to break off, such as the arms on the Z-bar. I once saw a Z-bar where the tube was cracking and bending right where the arms were welded on and the car had a problem just like the one described by the OP.