THIS^^^^^^^^Torsion bar keys are wrong or bars in wrong its only my opinion but thats all it can be.I can jack my tahoe up with the rear of the torsion bar it doesnt move yours are moving 3`4 inches just going in reverse and i see it raising the control arms.Alignment will be fine if your not putting that torsion bar under stress like i see it is.When you turn your torsion bar screw up or down i changes you alignment drastically im sticking with that.Put a block of wood on rear of torsion and slowly jack it up bet it moves up alot.Your keys can be indexed wrong its in their take them out again-make sure their the right ones.
You said the toe and camber get all messed up when in reverse. The toe looks off because the camber is so far off because of the torsion bar problems. @corvette744 is all over this.