Another question here:
If I take SAS flight from TXL to HEL which has a layover in ARN, since SAS has a minimum of 600 miles credited on A3 in the selected categories, I'd get 1200 miles for that trip? Because if yes then I think I can close this with a MXP - ATH - TXL - HEL - FCO. Is there a tool to get the right amount of miles?

I may do this:
MXP-ATH-TXL in Y A3
TXL - HEL with stop in ARN in E+ (1200+1200 M+B if I'm not wrong)
HEL - FCO with Norwegian.
Roughly 370€ even if I'm not super convinced