This route may seem a bit long-and-winding.. but it's the kind of habit I've got into, until someone comes along and points out what I've been missing all along...
Select one of the edges you will not want, and the next in sequence.
CtrlShiftNumpad + 'Select Next Active', until the interval-selection is complete
Header > Select > Loops > 'Edge ...
Create a plane, rotate it so it matches your perspective, and subdivide it so the quads match the big cells:
Then subdivide it again so it matches the small cells:
Of course you could subdivide it in a single step (39 cuts), but since a big cell always consists of 10 small cells and requires 9 cuts, it's easier to do in in two steps.
Now go to Object Mode, ...
You're quite close to the correct workflow:
UV maps are a flat projection of the 3D mesh, where every face gets mapped into a 1 x 1 square (or rectangle), meaning that every UV vertex gets a value X (U) between 0 and 1 and a value Y (V) between 0 and 1.
UV maps travel with vertices, they are simply 2 numbers (U and V) that define a location into a square, ...
I've not run into any errors onward and the control works as intended!
I had to remove the “DEF_hips.001” bone as a child from the rest of the deformation rig.
Then I had to make it the parent of both the left and right def_hip bones so it controls everything from the hips downward.
Then I had to make “DEF_hips.001” the child of “CTRL_hips.001”.