Hello and welcome to Road trip America !

First off, here at RTA there is no such thing as "Another annoying tourist" as we are all like minded Road trip enthusiasts so no need for apologies. Although our main focus is based on Road trips in America our reach is far and wide, so just maybe someone can come along and help with your Norwegian questions from experience. Although I don't have those 'tools in my bag' a quick search suggests "Superplus 98ron"(Blyfri) is readily available in Norway. Another quick search regarding winter driving came with the following advice >
Norway. Each driver must ensure that the car can drive in winter weather. There is an indirect requirement that the car must carry a set of snow chains when driving in winter weather.
To avoid any situation that may cause you to get stuck is to use common sense by keeping up to date with the conditions (hotel television/Internet and searching out local knowledge) and to use common sense without uneccessary risk. Hope it works out for you !

Dave