It's been eons since I tested. Is it still the case that the SAT punishes you for guessing, but the ACT does not? Then take the ACT. There are strategies to help with questions you positively do not know the answer to, but they are not a substitute for learning and studying. I really would not let fear of a test keep me from doing what I want to do. There will always be things you fear - you must learn to overcome the fears if you hope to go far in life.
Let me know if you want my test-taking tips!