Final Draft should work with the OpenDyslexic font, an open source font designed to help folks with dyslexia work on text files.
You can download and install the OpenDyslexic font from their website by clicking here.
Once the font is installed, open Final Draft and follow the steps at this link to change the entire script to the OpenDyslexic font.
Please note that OpenDyslexic is a third-party font, and we cannot guarantee its functionality with every Final Draft feature and iteration.