It appears one of the pads has worn down to the sensor... (time for new brake pads). The difference in response between forward and reverse may simply be a servo effect of the system.
Unless the rotors have deep scoring or ridging, I'd leave them as is, assuming the average thickness is comfortably above minimum spec. If you have the patience and really want to remove the ridge, you may try filing it off with a crosscut roughing file.
The difference in thickness between new and discard is not a whole (25 mm vs 23 mm) for my car. Most posters here report that it's better to buy new rotors than turn old ones.
95 E320 Cabriolet, 131K