Hey Tim,
Thanks for reaching out to us and sorry to hear about this issue 🙁
While your points sounds super valid, it would be great to discard conflicts -with the theme or other plugins- before jumping into it. Is it possible for you to test this -maybe in a staging site- with default TweentyFifteen WordPress theme and no other plugins active? If this could happen in the same server that would be a plus for sure.
Also did you notice this slowdown happening after a plugin or theme upgrade? Have you tried using any caching solution on the site? The number of events you are running seems a bit high and maybe some caching helps the overall performance.
Please let me know about those,
Best,
Nico