#2) if the choice is between "too tight" or "too loose"... go to a different store that sells a different line of helmets. every amnufacturer builds to a different shell, and sometimes more than one within a brand (I have several AGVs, and they all fit a bit differently, and all are the same size).
Your final fit should pretty much be Goldilocks- "just right". if it's a FF lid, maybe a tad snug in the cheek pads. everywhere else should fit correctly, right from the get-go. the padding around the majority of the shell has very little real give to it. when it finally stretches out- it's time to be replaced.