Why does "Ruler of Armenia" contribute 1% to my threat whereas the other king titles and my empire title does not? I'm not even holding the title king of Armenia anymore I gave to one of my vassals.
You are receiving 1% Threat from being the Liege of Armenia. When a vassal (such as your King of Armenia) generates Threat a portion of that Threat is also added to their liege. Odds are the King of Armenia recently won a relatively small war that expanded his territory (or inherited land, or vassalized someone).