You need to add the widths and heights to the position rather than just absolutely setting it relative to the layer/ group.
You just need to re-think the logic of this a little bit.
If the corner of the box needs to be locked to a corner of your safe area, that's what should be driving the positioning, not the text.
Box gets dimensions from text.
Text is parented to box.
Box anchor point is locked to bottom left/right corner of itself.
Box position is locked to the bottom left/right corner of safe area.
While it would certainly be possible to create one rig that does both left/right, I think it's much simpler to just make two setups, one for each side.
(I added a few static expressions just to keep the positions locked in place/avoid accidental dragging.)
Here's a rig that should work for the left, regardless of how much text you have in here. Let me know if you don't understand how to adapt it for the right side.
Thanks so much Kyle! That worked wonderfully. I was able to switch it to the right no problem.