You are there with your chicken. I am not. Only you can be the judge whether the flap is still viable (alive). It sounds from your description that it may no longer be of any use if it has no flexibility. But it would be worth trying anyway if you aren't sure.
To get the flap to stay in place, use a lot of Bag Balm, first on the wound, then over the top of the flap which will hold the flap down. You may need to reapply the ointment a few times before it stays down. By the third or fourth day, if the flap is viable, it will "take". Keep putting the ointment on it every day until it's healed.