Sorry to hear about your bad experiences. Liner pools really are pretty good and have some distinct advantages. Chemically inert and when they really get bad looking replace the liner and the pool looks new, and they are more tolerant of slight settling. But..they are prone to punctures, critters, and tears and that's why public pools are not vinyl.
On your plan to fill when it passes the returns and light....wise. I mentioned in a post a long time ago that knowing the change in leak rate can give an indication of the depth of the leak. Using a ruler or something similar, measure the water level to some known and repeatable reference like the top or bottom of skimmer, a specific point on a step, etc. Measure as accurately as possible every few hours. If the level is approaching the leak point the leak rate will slow. If the leak is at the bottom, like mine was, the rate won't measureably change. Once I knew mine was at the bottom of the deep end it didn't take long with dye to find the tiny slits that were leaking about 50 gal/hr.
Al