I have to say, I always admire an adventurer, to some your plan would seem, foolhardy or even bloody stupid. I think you need as you have said, to really do an in depth risk assessment, from all the info given by people here and do in depth research.
You would be surprised by the amount of people who you see cycling through Norway during the winter months ( Locals I would point out).. You need to choose your routes well, as some roads are snow ploughed to the tarmac surface, some; well the greater percent are only ploughed to provide a useable surface. As has been pointed out to you the HGV traffic will cut deep groves, which help the truckers to keep their trucks on the road. For sure if the police think it is unwise for you to use a road they will stop you.
You biggest problem is going to be the cold, and believe me cold kills very slowly and silently.
The locals who cycle wear a vast arrangement of different wear, but basically they work to the layer system, base layer, intermediate layers, and wind proof outer layer, that include the head which can lose 70% of body heat, because we have major arteries and veins passing through the neck. Most of us UK cyclist already practice in winter riding and understand the layer principles, for Norway you just need to have bigger and better layers..
During the winter Norway does not get that cold, a maximum high on average being minus 5-6 deg C and a minimum on average -16, a temperature the human body can handle quite well.
What is the problem is the wind-chill factor, as an example: if you cycle at Minus 5 deg C at 20 Km/ph you will experience a wind chill factor of Minus 20 deg C. At Minus 16 deg C at 20 Km/Ph you will experience a wind chill factor of Minus 30 Deg C at that wind chill factor your flesh will freeze in one minute. Very easy to not notice the onset of frostnip and frostbite.
Likewise, your bike will be subject to the same factors, rubber cracks like human flesh, grease likewise has to be chosen to allow for the cold, alloy parts become brittle
Cycling by yourself would in my opinion be extremely foolhardy, so easy to get sideswiped by a truck or car, and no one would be any the wiser.
I can only say good luck in your adventure, just remember a lot of cyclist have come up in the past with what the majority consider to be foolhardy, but have gone ahead with it and proven them wrong.