Sorry, I'm confused. Your final question was:
why the actual order notification is not being received
Do you mean the webhook for an orders/create event being triggered? That's a different webhook subscription than fulfillment webhooks.
As for Step 6, what do you mean as to:
I then sent the fulfillment from shopify admin
Do you mean you clicked the Mark as fulfilled button? If you subscribe to the fulfillments/create webhook then if it's an API-created subscription that means it isn't visible in the Shopify admin. Per the Shopify documentation:
You can configure a webhook using the API or in the Shopify admin. Webhooks created using the API do not show up in the admin.
But even then, regardless of the webhook's visibility in the Shopify admin the webhook should still fire when you clicked the button. Hopefully someone from Shopify can weigh in on this message thread. Sorry I wasn't of more help with your challenge!