Wow…once again I may have wasted hours of my life on no-thing. I was going through this whole screenshot-ridden description of my exact steps when it occurred to me that I was moving the bones in Edit mode, not Pose mode, to check the rig and that’s when I found it broken. I’m coming to Blender from Maya, and I can actually assure everyone that I think Blender is the better software for a million reasons, but it is not remotely intuitive. In Maya, this is not how rigs would function. The flipside of this is that in Maya, rigs broke very easily when you forced them to do things that they wouldn’t let you do by default. Rigs are far more flexible in Blender after being painted.
Anyway, let me try the rest of this now, which I actually think is going to work, and we can probably end this thread on a high note after that. Thanks again, mate.