Is there a way to back up all of my style sheets?

You can back up style sheets individually or all at once. To back up any individual style, click 'Manage Styles', then select the style sheet and click 'Export'. To back up all styles at once, find and copy the equivalent of this file on your computer:

C:\Users\[Your User Name]\​AppData\​Local\​PerfectIt5\​PerfectIt.Styles.sdb