The provenance of this lonely viking spearhead is golden. It certainly supports the Kensington artifact as well. From this it becomes clear that viking traders penetrated the Great lakes region by way of the Hudson and surely the St Lawrence. There is zero indication of permanent settlement but that seems unlikely anyway when they had the entire Atlantic Coast to work with along with the Arctic and even the Pacific Northwest.
What everyone fails to recall is that a viking long boat could be readily manhandled overland if it became useful. Hard work of course, but scouting a land passage was no problem and your manpower was sufficient to even lift the boat if necessary. thus cutting a portage path and laying down runners is completely plausible.
I have no doubt that the Northwest passage was easily forced by an overland portage over Banks island in the Arctic..