Ok well I understand the feeling of dread and frustration but I'd resist digging just yet. One good indicator is the rate of the leak over time as it will slow down when the level gets closer to the hole. I assume you mean you lost 3/4" more than what the bucket test showed in evaporation. I could see the vacuum issue indicating a problem if it was pulling air from a crack in the pipe when the suction became higher and you might well have more than one issue or the water is leaking out the skimmer line. I plugged everything I could on my pool and measured the loss. I put plugs in my returns, my main drain, and my skimmer. If your below your skimmer now then just wait another day and see what happens. Mark the level with a pencil on the stairs if you have stairs or attach a ruler to a fixed part ..main idea is to accurately track the rate of loss so you can tell if it's slowing down or has stopped. If it slows then you start looking around the pool just below the water line etc. I came to understand that this was going to be a week or two project for me and was about to call someone to check my liner with a hydophone. It cost 300 bucks here and they put an electrical charge in the pool and then check the magnetic field which points to the leak. The liner is a good insulator except where it's torn as the field gets grounded by the water going out the hole. Luckily I stuck with it another day and found it myself. Let us know how you're getting on.