If every checklist fails to make things work, I would open crossfeeds, do anything to help the situation no matter what the checklist says and doesn't work. Especially like this when you have no time to read a checklist. They were probably thinking outside the box because that is all they had left. If he brought the flaps up to 20 he probably saved everybody but no checklist says to do that at 600 ft. He did a great job.