Advice on Changing Pads in a Parking lot

Proportioning is not left to right, it's the ratio front to rear. If it's pulling there's a problem in the brakes or as you say, a bent frame. If the frame / alignment is OK, pulling can be rotor finish/ damage, stuck pistons, problems with tubing and fittings or even fluid or grease on the pads

So far as turning rotors "or not" it is impossible, really, to tell by looking. Rotors must have parallel finished sides, AKA not tapered, and both have a reasonably even "same as" the other finish. The other little "gotcha" is the ridge outer/ inner. This wears as the pads/ rotors wear, and new pads wont "sit" on the pads quite right in that case

The short answer is, sometimes you can get away with it, and sometimes not