While it seems like Yukimura might be going historically accurate, there are still so many things that could happen here. I had a pit in my stomach that just never went away ever since chapter 177, when it’s shown a rat is on the ship, and Vargar mentions it’s good luck. It still hasn’t gone away, regardless, there will be heartbreak. Wether war comes to fruition, or they just leave and the Vinland experiment comes to fail, or they make amends but Lnu continue to pass to the disease, there is no clean way out of this.