Yes, I used a "drain tool". It was a pair of channel locks turned upside down. I tried to turn it with just my hands and broke one of the cross hair members. I'll buy a drain tool today and try again tomorrow. My plan is to apply some heat to the drain and then try with the drain tool after a small cooling time.
The tiler is going to float the tile. Otherwise I'd give your suggestion a try.
Lastly, I demo'ed the drywall out to the stud. About 18" down from the ceiling, I measured the distance from the exposed stud to the next, covered stud. Then I added 7/8" to put a cut right in the middle of the 2x4. I drew a perpendicular line to that measurement and made a ceiling to floor cut along the line. My cut came out basically perpendicular.
Unfortunately, unlike all the other exposed studs, this on is not perpendicular. At the ceiling, 1/4" of the stud is exposed. At 18" down from the ceiling where I measured, it's right in the middle of the stud. At the floor, there is a 1 5/8" gap from the drywall to the stud. That's how much it leans.
Nothing like good old American craftsmanship, and this was in 1957 or 58, when American craftsmanship was supposed to be good.
Pictures to follow.