You say above you are now using the modified iancoleman tool to try to find the former adresses/keys. But with the tool have you already been able to get the same adresses and keys you currently have on your Electrum wallet with your seed?
I could get the addresses but only from the left wallet >>>>look at the picture from @BitMover
The left wallet is the seed without BIP39 check
The right one is with BIP39 check box - from that one I wasn't able to find the address until now.
Keep in Mind both were generated using the same seed & I can recover the right wallet anytime using this derivation path: m/44'/0'/0'