...You should connect your Electrum server with your full node and then your Electrum client with your Electrum server. Now you can create a wallet by importing private keys and it'll return you their balances.
If you have any questions tell me. I'm willing to help you achieve all the above, I just find it honestly a loss of time for you....
Although as you said it's pointless no matter what, for efficiency it would probably be easier to write something the queried the electrumx database directly instead of using the client.
If you don't mind slightly old data, with the dump that loyce has it is simple to put it into some db and just run queries.
For more efficiency still just import the addresses, you don't need the amounts. Once you match a funded address you then look at a live explorer to see if there is anything there.
Still as waste of time......
-Dave