As far as what territory the Norse would occupy if a long-term settlement did get established, they would probably take an islands-first approach. Why? They've done it before, rather successfully. Take a look at this map of the Kingdom of Man and the Isles:
http://en.wikipedia.org/wiki/File:Kingdom_of_Mann_and_the_Isles-en.svg
Yes, but for a reason.
They were dealing in Europe with native opponents who were numerous, dangerous and moved well on land - but inefficient on water.
The Skraelings are much less numerous. And they travel by canoe, too. So the Norse do not have the same danger in settling on mainland, and for the level of danger they do pose, narrow straits of water are not so much a relative protection.
Now compare it to this map of the Gulf of St. Lawrence:
http://mappingcenter.esri.com/index.cfm?fa=maps.stLawrence&effect=View PDF
I would expect that they would set up shop on St. Pierre and Miquelon early on. They likely would eventually take over all of Newfoundland, but perhaps not before they take Anticosti Island, Prince Edward Island, the Magdalen Islands, and Cape Breton Island.
IMO, they are not particularly attractive for Norse. They offer nothing Newfoundland does not already have.
Once they have these and Newfoundland, then a push onto the mainland begins, and it would almost certainly involve exploration up the St. Lawrence. For the Norse, water is a connector, a highway, not much of a barrier at all. Any established presence would expand outward from these island bases.
Water is a connector. What is a barrier is rapids.
The Norse would sail as far as Lachine rapids. Their ships cannot go on.
On Atlantic coast, they can simply sail on to next inlet, river, bay, on their same knarrs, as far as Florida and Yucatan. Not on St. Lawrence.
They want to go on. There is the huge market of Great Lakes and Mississippi Culture beyond Lachine.
So the Norse have to get off their high ships - explore the shores, chop a portage road through the forests and around rocks, beach their knarrs and build new, smaller river bateaux above the rapids. And they have to negotiate with the neighbouring Skraelings so they would not get ambushed while stuck on portage.
Montreal is where they need to settle - which they do not need on Gulf of St. Lawrence or Atlantic coast.
Mind you, islands still have an advantage. The island of Montreal is not defensible. A determined Skraeling war party on a raid would easily row their canoes across the narrow rivers anywhere along the tens of km of island shores, and the small bunch of Norse could not even keep watchmen to alert them of crossing, let alone post an overwhelming defensive force at whatever spot the Skraelings do cross at. But the island is demarcable. If the Skraelings negotiate with Norse and promise not to trespass on the island then they cannot go hunting on Norse cows grazing on the island and when confronted, claim to have got lost chasing a moose. Nor can they bring complaints of Icelandic horses trespassing to eat their maize fields if the horses are known not to swim St. Lawrence just for greener pastures.
So... how about a bunch of Norse buying/renting the whole island of Montreal? The local Skraelings can keep their maize fields across the river, they will not be molested by Norse sheep grazing on their fields and they get some rent for the deal, like mutton, cheese, butter, iron axes... and in addition to Isle of Montreal, they allow the Norse to sail on to lake Ontario, trade on both sides of river and get Skraeling guides and interpreters on their trading expeditions. Would the Norse do that?
But minor details...