There is simple solution to DK’s hostility, which however requires use of earlier gamesave (before player jumped via hypergate into Inner Core System). Killing ancient drone ships in Dervon (which is part of the story!) makes DK friendly. Reason (potential) why they aren’t ’green’ may be extensive killing of Nomad’s ships, that’s all.
Another possibilities (why things go wrong) are modded game files, use of autosave or not follow of campaign script) … with all those plays which I did myself, only autosaves use was real danger when I simply played SP campaign and followed it’s given path.