3xC Return in Sweden with Booking Class J/Z/C/D
Costs ca. 3500-4000 SEK/Trip. Earns 1200+300 EBG per segment.
Possible to do on 1day.
Same should work with ARN-Zone 2 (ZRH etc) as Eco Return x 3.
Domestic C-class gives 1000 points nowadays, and OP is EBS (i.e. +150 per segment). So 3 domestic round-trips in J/Z/C/D without stopovers would only give 6900 points.
I'd have a look at flights to Greece, Israel, Malta, Portugal, Spain and Turkey instead since these give 2000 in M, 3000 in Y and 4000 in C. Including a stopover in CPH (+500/750/1000 points) and EBS-bonus (+15%) that would be 5750 / 8625 / 11500 points for a round-trip depending on class. So if the OP manages to squeeze in an extra domestic stopover (for example by flying LLA-ARN-CPH-BCN/MAD/ATH/TLV) a round-trip in Economy Extra would do the trick.