The main assessment of the project will be the mini–biographies that students write at the end of the simulation. This is very important as it will amass all the work the students have done and challenge them personally to connect with the material. I would also make several mini–assessments and check–ins of the different phases. This will help you keep track of students' progress and learning as they go through the project.
To grade the final written assessment, I would recommend using a broad definitions and categories. This will differentiate the way students are assessed and give them multiple avenues for success so that you aren't relying on one or two assignments to determine their entire grade. Pass out all the rubrics before starting the project so that students will know what they are being graded on and expected to do. I would also distribute a projected timeline to help students not feel overwhelmed about this project.