The assumption is that with enough exams for each student, uncertainties will average nearly to zero. Students often come to my office especially after the first or second exam to say they are very concerned about their performance in the course and want to know what they can do to get a better grade. I appreciate it when students come to see me because I want to understand your situation and any difficulties you are having, but these discussions are often frustrating because there's not much advice I can offer beyond what I have already said. It's not as if there is some magic prescription for learning the material that I have kept secret from you. There is no substitute for hard work and practice.
Students sometimes ask if there is work they can do for extra credit.
Although I applaud your willingness to do extra work, the course is hard enough without my inventing additional things for you to do. The best extra work you can do is to solve more problems, and the extra credit is in the form of a better performance on the exams. It wouldn't be fair to the other students to grade you by a different standard, to change the rules in the middle of the game, or to give you opportunities to enhance your grade that are not generally available to everyone. You might try making up practice exams for yourself using problems from the text and working them in the allotted time using only the allowed aids. There's always a debate over whether grading should be done on an absolute scale or on a curve.