Hello Isobel,
You are correct that you need the Facebook add-on to import events from Facebook into your WordPress site. That add on requires the free The Events Calendar plugin, which it sounds like you already have. And to be clear, it imports events from Facebook, it doesn’t synchronize them or push them over to Facebook.
I don’t know of any conflicts with the theme you mentioned, but I’m not familiar with the theme either. You can have a look at our Facebook Events Primer (https://theeventscalendar.com/support/documentation/facebook-importer-new-user-primer/) to get a better feel for what it can, and can’t, do.
As for refunds, you can see our policy on our FAQ page (https://theeventscalendar.com/support/faqs/).
If I can help you with anything else, please let me know.
— Julie