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.
This is exactly my thoughts about the OP's issues here. I mean you own a lot of
BTC and it seems that you don't know how to even import or sweep your privatekey in other wallet software? Something is not right here, just saying.
May be it's true. But back in the days, it was easy to mine and less technical knowledge was required than now. Or may be OP has bought this big amount when the price was low.
However, I too think OP don't have such much amount of BTC, it's a bug possibly.