Hi Eric, sorry for not replying to your email yet, but I'm glad you've discovered the Q&A forum to ask your question.
What you're trying to do is achievable with SEQUEmatic. I've taken a look at your sequence, and you will need to add the parameter name Event in parameter 1 of the webhook step.
After that, the sequence should work as you expect. You might also like to use the contains comparison if the paramter doesn't match your check exactly.
Let me know if you need any further help.