-- Question...without knowing what valving you have is there any water coming out the waste (backwash) line if you have one, with the pump running? If so, probably a bad valve or valve gasket. Some people don't notice this leak source if the waste line dumps into a drain or something.
-- Suggestion...Let it continue to drop and see if it keeps going below the skimmer.
-- Suggestion...plug the return(s) and maybe the skimmer and see what happens.

-- Info...some adhesives can drive you nuts when trying to place a patch because they aggressively attack the vinyl patch and curl it before you can place it in position. Boxer adhesives #100, available at most pool stores, is a slow acting and therefore slow curing adhesive that will not curl the patch quickly.

Hope this helps.
Al