You PM'ed me that you found your seed and xprv inside the wallet file. Did importing them the way I said work?

Forget exporting private keys and other stuffs, the (wallet file corruption detected) 1st error's "suggestion" will fix your problem.
Only very OLD versions of Electrum have a ".dat" extension, was that from a very old version?
Otherwise, it isn't an Electrum wallet file.

Try to open another copy of the original electrum/wallet.dat (not the previous one that you've opened) using the lowest version v1.8.1 available here.
Then either extract the SEED or export the private keys to be imported to the latest version.

This is a generic error message, you can disregard this one.
..next line

This often pop-up if there's a problem with your transaction's signature or inputs.
Maybe it came from a non-existing address with huge balance that was caused by the "wallet corruption error" that you've seen during startup. (from your screenshots)
Your corrupted wallet might have signed the tx using an invalid private key and/or there's an unspendable input included.

Just download it for your platform from here (https://www.coinomi.com/en/downloads/) >> install >> restore wallet.

You do have private keys/seed, right? Cause I'm bit confused with previous comments here.

Can you try importing your private key into Coinomi wallet (https://www.coinomi.com/en/downloads/) and update us if it works?

As long as you have private key, you should be able to access your coins anywhere. I suggested Coinomi as I have been using it, you are free to choose other wallet as well.

Also, if you encounter any trouble restoring your wallet in Coinomi, feel free to contact me. I'll help if I can.

If it's empty, then... it's empty. Again, where did you get this wallet from? Is it really yours? Did you create and deposited/mined these coins or something like this? Not many people supposedly have 33k BTC in a wallet. Actually, according to this[1] site, only 106 addresses have 10k+ BTC (most are inactive).

[1] https://bitinfocharts.com/top-100-richest-bitcoin-addresses.html

first of all to be sure you have the correct Electrum wallet and not a malicious one you must verify its digital signature with the correct public key of the developer. checking your history,... is not a proof!

as for the failure to broadcast that transaction, it is simply because it is an invalid transaction and the server error is pretty clear. it is most probably because the public key provided inside the scriptsig is not the same public key that exists in the scriptpubkey (the hash of it) which is why it fails on OP_EqualVerify step.
try signing the transaction with the correct private key instead!
and if you really did that, then post the raw transaction here and i can tell you exactly what you did wrong.

Simply right click the wallet file, select "Open with" and choose the Notepad or any other text editor.

But please, answer my other questions. Search for the address on the blockexplorer to see if the balance is there and tell me how the addresses look like before (right now on your Electrum) and after the import with the private-key.

first of all to be sure you have the correct Electrum wallet and not a malicious one you must verify its digital signature with the correct public key of the developer. checking your history,... is not a proof!

as for the failure to broadcast that transaction, it is simply because it is an invalid transaction and the server error is pretty clear. it is most probably because the public key provided inside the scriptsig is not the same public key that exists in the scriptpubkey (the hash of it) which is why it fails on OP_EqualVerify step.
try signing the transaction with the correct private key instead!
and if you really did that, then post the raw transaction here and i can tell you exactly what you did wrong.

1. If you search for this address in a block explorer, do you see your balance, or is it empty? Try it: https://live.blockcypher.com/
2. How does your address look like? It starts with a 1, 3 or btc1? And after you import the private key, do they look the same way (starting with 1, 3 or btc1 just like your current wallet) or it's different?
3. Click on Wallet -> Seed, see if your seed is there. If it is, copy it and create a new wallet by restoring it with it. If it's not, try opening your wallet file in a text editor and look for "seed" or "xprv".

Do you have an address where coins are stored? If so, try exporting the private keys and install a fresh wallet. Import those private key into the new wallet.
Have back up of the wallet file, don't do any silly mistake if you have such numbers of coin in reality.

You didn't say if you had updated this or if this was a fresh install, here is a link to a thread with the same error- https://bitcointalk.org/index.php?topic=5159481.0

It seems like their issue was down to trying to use an incorrect bitcoin core wallet dat in their electrum file section (I'm pretty sure) Have you ever had an install on this machine previously?

With the keen eye of TryNinja this seems to be your issue. Now I am just stuck wondering if you're a whale and truly have this large coin amount.

Hmm... so... do you really have a balance of 331831 BTC in your wallet? Something doesn't seem right here. Where did you get this wallet from?

Is this really an Electrum wallet? I see it has a ".dat" extension (or that's just its name) on the wallet file, which would be a Bitcoin Core wallet.

Are you sure? Check your history, did you click a link or type it in? If you typed it in are you sure it was spelled correctly?

If this is just an error, what changes have you made since installing? Any changes in the settings? Did you click any options? Things like that will need to be known to further help.

Where did you download the electrum from? It should NOT be asking you for you to reenter your seed, that seems EXTREMELY suspicious to me. Is this using a hardware wallet or is it a standard digital wallet where your coins are held?