ahh, the missing teacher explains a lot!
Seriously though, use any free time to go through online resources, you are obviously an excellent student, you may still be able to pull off a decent score
(Also, for the long-term sub, if you really do end up doing poorly, you may ask counselor to mention in their recommendation that situation and that is why a score was out of norms).
Also, another thought, do you HAVE to take the exams? A missing exam will be less of a flag than a 1. I know some high schools require you take them though…