Am I missing something here?
Your screenshot already shows the simple formula on how to compute the absolute fee.
If you want to minimize it; set the fee rate to the current optimal which is that 12sat/vB in your other screenshot (same thing you'll get with "mempool" slider at '0.8mb from tip')
And more importantly, select only a few large UTXOs since your transaction probably used a lot of inputs for reaching 2045vB size.
To do that: enable and go to 'Coins' tab (View->Show Coins), multi-select some UTXO that are enough to pay your recipient, right-click and select "Add to coin control".