If you connected to your Electrum server via LAN through port 50002, your ISP won't know a thing.

I think it's pretty clear that if you want to personally use your electrum server, there's isn't such much point to do it through tor; your Bitcoin node could then broadcast your transaction through tor, but transferring the signed transaction from the Electrum server to your Bitcoin node through tor while both run under the same router makes things more complex and provides the same privacy.