Wow. Finding a small leak in a liner is hard.

On a pool your size (thanks for completing the chart!), a 1" leak per day is only about 120 gallons, or 5 gallons per hour. That's a fast drip.

There are 3 ways to find it that I know of:
1. Find it on the outside, where the water is coming through. Sounds like you've already checked all the exposed outside.
2. Let it leak till it stops; usually the leak will be within an inch of the water line. You could speed up the process by pump out 12", and seeing if it still leaks, then 12" more and see if it leaks. The leak will be in the LAST 12 band you check. Refill 6" and see if it leaks. etc.
3. Get in the pool with a mask and snorkel and look for pinholes or bad seams. If your pool walls are steel, you might feel for rusted steel under the liner, too.