These are some of the possible errors I can think of, beyond what you have suggested.

I do think I have downloaded the entire blockchain as every time I open Bitcoin Core it has to do the last 20-48-128 blocks before it starts up, it seems.

The thing that was sent 11 days ago I THOUGHT was from a completely different wallet.dat account, but maybe somehow it is the same??? I dont understand how this is connected.

Maybe I am somehow mixing accounts up. I have found in my old hard drives 10-15 old wallet.dat files. Some are certanly the same, backups of backups.
I have opened them all by exchanging the wallet.dat file on my MacBook. And then restarting the Bitcoin Core client to see the content of the new wallet.dat file.
And then after looking at it giving the old ones other temporary names like from wallet.dat to walletfromoldtoshibalaptopwallet.dat etc after I have tested them.
Maybe somehow the opening of these 10-15 different wallet files has messed up the entire Bitcoin Core client for me.

Or that what I am seeing is different stages of the same accounts somehow...

For me I cant seem to be able to differentiate them by unique addresses...

I have now bough a brand new MacBook that I intend to setup exclusively for crypto purposes. I intend to download Bitcoin Core to this and try to open only the btc X.98 wallet.dat file on that instance of Bitcoin Core, to see if that works better (but I should not try sending anything as it seems it is the sending that is extracting these massive fees).

I will try to send something TO that account before I try to send anything more off from it.

That somehow the BitcoinCore client is processing things from one wallet.dat file on another wallet.dat file.

That I have somehow done the settings wrong, so that I have changed to 2 blocks and this for some reason comes with massive fees. Or some other error I have made.

The last thing is that I somehow do not understand this Bitcoin, address, account, wallet,  Bitcoin Core,  thing properly. I think I understand it, but I could be misunderstanding the whole account address wallet thing. I see from my ledger that there must be something I do not understand.
I find it hard to understand how to find on Blockchain the content of my Bitcoin account as I see them in my Bitcoin Core client and my Ledger client. It seems to work different from Ethereum. I am quite confused. Can one account have more than one account address???

My apologies for unclear language.