In your config you have 4 outputs. If you only have one Decklink card you can get rid of the rest. With the Decklink SDI 4K card you will not be able to output fill and key. So the keyer setting should be set to Default. The whole channel block should look like that:
You can probably also remove the screen consumer node. By the way, as soon as you define your Decklink in the config it is occupied and can not be used a input. So the Decklink Input command in your screenshot will fail.