I understand how you feel. And I'm glad the original pool guy did the right thing by not charging you. If he did use a garden hose and bladder at first then at least he understood the dangers of pressurizing PVC with gas. I sincerely doubt that your efforts caused the leak, but perhaps a combination of events has lead you to where you are.

Pools (like any other part of real estate) do become a money pit over time. Anyone with an "old" house knows what it's like to have to constantly repair failing infrastructure year-in and year-out. It would be sad if you drained your pool and just had an open pit in the backyard. In fact, you might not want to do that as draining a pool can also cause damage that would then make your home more expensive to sell in the future. Tearing out a pool and backfilling the hole is expensive as well (~$10k-$15k in some areas) so your best bet may be just to keep it running as best you can until the day comes when you're ready to sell and move on.

Hopefully you'll find the leak and it will be something simple to fix. I'll keep my virtual fingers crossed for you...good luck!