I agree with Olaf, increase the temperature. I usually print ABS at 268 degrees but it really depends on the filament. Make sure you've got an all metal hot end before trying temperatures above 240 degrees.
Extrusion looks good to me, I'd keep the settings you use for now.
The sagging is probably due to the infill not being bridged properly, either increase the infill or add more solid top layers in the slicer. You can try a bridging calibration test (thingiverse has many available). I've set the bridging speed the same as perimeter speed, you don't want it to slow down as the pressure build up of a faster speed just before bridging extrudes more filament, causing it to sag. A cooling fan helps against sagging, even for ABS, which typically you don't want a fan blowing over the print because of warping. You can setup the slicer to turn on the fan only for bridging.
As for the blob, yes it's retraction amount and it can also be the speed of the retraction. The longer the nozzle stays still, the more filament is leaking out. I've recently calibrated my retractions and found that lowering the retraction acceleration from 3000mm/s2 to 2000mm/s2 I could set the retraction speed from 28mm/s to 65mm/s without the stepper motor stalling, which nearly completely solved the blob issue (a blob of 1mm still remains). The retraction length was 5mm and now use 3.5mm. So the retraction speed really helps to get the pressure off the nozzle. BTW, I'm using a bowden setup.
If you test retractions, it's better to print a non infill cube, just a single wall empty cube will do the trick, prints faster and wastes less filament. Testing bridging you can lower the height of the cube or use a dedicated part to test bridging.
