Most of these guys have been printing much longer than i, but if it were me, i would ease back on the extrusion width. If you have a .4mm nozzle and a .2mm layer height, keep your extrusion width at .4 and dial it in from there. I know it makes theoretical sense that since the extruder is orthogonal to the motion path, it shouldn't matter--the reality is that the plastic has viscosity and extruding over your nozzle width will always result in "pulling or squishing" effects which are difficult to control.
I would agree that the prints appear to be under-extruded and increasing your extrusion multiplier is an easy first step, but i would first decrease your extrusion width.
Looking more closely at your prints, you may just want to decrease your "Minimum Infill Length" to something very small. The hollow curves indicate that this may be your only problem. If you are getting separation between outlines or infill, then decrease extrusion width/increase multiplier. If curves are your only issue, then reduce this Minimum Infill Length.