FWIW,
Going back south again, you have to proceed on the E6 for a while, but as you proceed further westbound there are optional roads. The roads will bring you to some scenic areas, but also boring sections. However, if time is available, at least, touring the island Senja is worth while.
Whatever your choice, you will have to go by ferries, and some of he ferries does not go that often.
This website offers all the timetables for the northern ferries:
https://nordnorge.com/EN-svalbard/?News=157
Also, if time permits, road 17 from Bodø going south is worthwhile. These ferries go more frequently. This site list the timetables.
https://www.visitnorway.com/places-to-go/trondelag/kystriksveien/getting-here/ferries-express-boats-along-the-coastal-route-kystriksveien/?lang=uk