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

You can backup style sheets individually or all at once. To backup any individual style, click 'Manage Styles', then select the style sheet and click 'Export'. To backup 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