Webhook delivery delay, retry schedule, and alerts when a subscription is disabled

Hi, I build a booking flow for a client on the Standard plan. A user scoped webhook subscription listens for invitee.created and invitee.canceled, and our server books the paid session from invitee.created.

Three questions:

1. What delivery delay should we expect for invitee.created in normal operation?
2. Is the retry schedule still 24 hours with back off (as in the Dec 2023 staff post), and what happens to an event after the last retry?
3. When a subscription is disabled after failed deliveries, is there any alert (an email or an API field), or must we poll GET /webhook_subscriptions to find out?

Thanks.