I think it depends on the level of complexity you want your story to have. Complexity, especially in the fantasy genre, is not necessarily a vice.
As far as swords and the like, if you go with naming them something other than sword/bow/whatever, you'll have to go into a full description of the item in question and whatever the name is. Can you describe a sword or a bow using only words and no real starting reference? It's harder than you might think. And working those descriptions into the story might not be worth the work. Using the common names for items usually makes it easier and immediately conjures the image you want. But again, it depends on what level of complexity you want in your story.
As far as the crazy norse names, some are ok. Some are not. If something seems hard for you to remember while you're writing the story, it's not going to be easier to remember it as a reader. You really don't want people flipping back and forth through the book saying "what was the Grutrtrtinblurghinstein again?" If that's the case, change it to something norse-sounding that's a bit simpler, for instance Grutrtrtinblurghinstein could be shortened to gru, or grutin, or blurgh. OR changed completely to something else.
Another option to prevent readers from flipping back and forth is to reexplain what the weird sounding word means. For instance when you introduce the term "Njorthrbiartr" explain however you want what it means. Then when it's used again you can say something along the lines of "the heroic act that earned Dave the title of Njorthrbiartr" reminding readers cleverly what that term means without being blatant in your explanations.
Don't worry too much about pronunciations, readers will always pronounce things their own way. I mispronounced "aes sedai" for years until I heard the audio versions.
And you can always create a glossary at the end of the book with pronunciations.
But everyone will have a slightly different take. I think complex is fine if you have a good story. A complex good story for me is better than a simple good story.