Inaccurate circles/squares ...thoughts ?

All machines have defects, ones more than others, but even larger machines (5000 Kg machines) make defects, not so large as those that you showed, but in proportion to the machine quality.
This is where the cutting conditions come in and where the user head must help.

I would recommend to make your cutting and leave a finish pass (or more than one), so that the finish does not force your machine structure more than it is supposed to.
All this after the backlash is as tight as you can.

I just thought I would let everyone know, if there was anyone interested that after tightening up everything on the machine, it seems like I'm making (virtually) perfect circles now. I even built a stand for my mill, I wanted to out of aluminum, but settled for oak wood. Basically everything is super secure now, and what do you know it actually made a difference.

Thank you for all of the help.

Glad you got it sorted out.
Wood is good.

Rick G