The road from Goose Bay to Cartwright is completed as a great, fast gravel highway although it will be a side trip to get to Cartwright from the new road.
GB to next gas stop at Port Hope Simpson is 400km.
As for bringing a shotgun to protect against bears, not needed.However you might consider bringing cholesterol reducing drugs to feed the bears in case one does take a liking to one of you.
And watch out for the speed traps