Is it possible to configure the MoonBot terminal to trigger the urgent sale of all coins, if the BTC has fallen by more than a certain percentage?

Yes, to do this on the tab Settings – Autostart you need to put a tick in front of the parameter: “Global Panic Sell If BTC rate changed” and below after the parameter “Hourly BTC rate drops more then (%) +X.XX” in the field specify the desired BTC rate drop threshold in percentage.