Thanks for reaching out, sorry you are having trouble here. The 250k/month is a fleet-wide event limit. It represents the total number of outbound integration requests that can be sent each month. The issue you are running into here is slightly different, it is a rate limit on the frequency of webhooks being sent in a certain time interval. You can read about all the different webhook rate limits here: https://docs.particle.io/guide/tools-and-features/webhooks/#limits.
What I imagine you are running into is the limit by host. Across all webhooks in our system, we enforce a maximum of 120 requests per minute to a given host to avoid unintended abuse of a 3rd-party service. It would be helpful to know what URL you are using in your webhook, and we can look into why you are being rate limited.
Thanks!
Jeff