I hope he knocked a few dollars off the price for having you empty it for him. It's not a huge deal if it's not done, but it does save some hassles in the morning when you show up on the job. Like the ones you performed.

If the walls where going to go any time soon they would have when the water was emptied. It actually helps to remove the water very slowly as you did. You should be fine. Although I usually put a string line on them prior to emptying just to see if the they "bowed" a little. Sometimes they will bow a little then go back into place once the pool is refilled with water.

Good Luck......