is this the right pass?

It will ONLY-as the name says-cover the trains and these are just a very few in between a mass of buses and other means. It looks to me as not a very clever set up alltogether, as there are also NO trains between SE and FI that far north, plus that you DO have to double check times if you are determined to use trains: over north there mostly just 1/day and bad connections with bus. The trains that do run are meant to link to the capitals, like to STo or HELsinki

There are splendid local and national planners that combine train/bus/ferry/whatever over there, as could be expected from well-organised Scandinavian countries: SE-resplus, FI; Matkahuolta (which was long ago a monthly all-country printed timetable). Bus times can vary an awful lot per season there-and alas, around 12/12 is the EUR-wide major timetable change, so as by now it may not yet be avaialble. The borderpost FI-SE is named Haparanda//Haapaaranttaa and has a EU-sponsored brand new integrated bus/train station on the border, with a giant IKEA. Planners will only work for their own country.

I also hope you are aware that far north in that time there is NO daylight-just a hint of shimmer of light between 11-13 hr. The rest is just pitch-black night.

The Flamsbana gives only discount to passholders.