I'm following along on this adventure on the side as well so I am aware you've tried a few other things but you don't have an actual yoke tester.
You applied a DC voltage on a fixed current through the windings in the hopes of locating a hotspot but on the thermal camera it was quite uniform all around.
What is the diameter of the neck? Inch and a quarter? What is the model of the tube?
I just find it weird that so much of the neck is shorted out.
For context, initial tests found the HOT was extremely hot and the system power supply (which also powers the monitor) was being dragged down when the monitor was connected. Compu_85 pulled the HOT (C3412) and did not find it shorted. Likewise he found that a dummy load on the PSU didn't cause the pulldown, so it's absolutely the display. With the HOT installed and the yoke disconnected he doesn't see a heavy load on it and the PSU behaves. All we could think of was the yoke was funky and that's why we pulled it and started looking for shorts. Could be a dead-end but we're not totally sure.
Edited: ah, he ninja'd me below.