I hope you are well today and thank you for your question.
You can optimise your site speed as described on the following pages.
Additionally, I attempted to remove query strings from static resources with W3 Total Cache as Pingdom suggests, but when I try to download the W3 Total Cache plugin it says it has been blocked by theme creator?
No the theme doesn’t block it.
Could you please share the screenshot of the error that you are getting?