That simply is impossible since AES-256 (the encryption that Electrum uses) is a modern cipher which is resistant to known-plaintext attacks and it has been designed in a way to resist this type of attack specifically since in most use cases of it we already assume that the plaintext is known.
This is not a common situation, it's like an equation where we know 2 variables and the 3rd is unknown.
For example when an electrum wallet is crypted we got the following:
2 + 3 = X, we know that x is 5 cause we know the first 2 numbers, same with electrum when doing encryption:
unencrtyped_wallet + password_encryption = X,
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but in this case we got something like this:
2 + X = 5, we can also find X because X = 5 - 2
same should be applicable to my situation:
unecrypted_wallet + X = encrypted_wallet
I need to find password X by knowing the wallet in it's 2 states, both unecrypted and also encrypted with password X. On paper it sounds very do-able to me. We got 2 known parts of a 3 part equation.
BOTTOM LINE
I am looking at a very large sum of money, if anyone can pass my test I will pay that 0.1 which is literally nothing, the most important aspect is that we will continue in private where I present the winner of the test to the real situation.
Let's just say I will pay easily 30 BTC or whatever the price of a Lambo Aventador is.