He could also fly to Murmansk and cut the drive in half. Personally I'd fly to Murmansk, drive a couple of hours to Kirkenes, and spend a few lovely days taking the boat down the coast to Bergen before grabbing a train to Oslo.
Many things can happen on a small boat in the Atlantic at night.
Sure, but nothing that can't also happen in a car on a small backcountry road at night. And anyway if he takes a passenger ferry he'll be constantly surrounded by hundreds of other people which is a hell of a lot more collateral damage to take into consideration if you're genuinely concerned about someone causing an 'accident'.