A general narrative argument is a fine place to start.
But you should keep an open mind that through use of Dramatica, you may end up with a richer narrative argument that is more directly tied to the structure. This is what the narrative arguments found on Narrative First's Subtext service are -- ties to specific story points. But you can't really do that until you know your storyform AND have an excellent grasp on how the story points work in your particular story.
So, I feel that trying to reword and come up with a perfect narrative argument isn't that useful right now. It's putting the cart before the horse.
What you should do now is concentrate on understanding your four throughlines. Write a summary sentence for each one so that you can see them each as their own separate stories. They will be intertwined in your story, but in order to use Dramatica, it's important to see them all separately.