I tried FinderOuter but it’s taking more than a month and gives more than 100 private keys.
This is weird. With 11 missing characters, I'd expect much more valid private keys. If you know the address, you should know which one you need. But if you don't know the address, you should have many more private keys.
Anyway, with just 100 private keys, you could even import them into a new Electrum wallet to see if any of them have transactions. See
this post to restore Segwit addresses.