Do they all need to be in one module? Or could you have each CBT be a separate module, with the final test as a new module?
Otherwise, you would probably need to look at creating your own question slides for the Let Me quizzes at the end of each chapter, and use a variable to hold the score, with an advanced action at the end deciding if they continue or not. The final test could then be a normal graded quiz that reports to your LMS.