Sims 4: Get Scared Expansion Pack

Agreed...fire should not make a Sim tense, it should make them scared. Or scared and tense. Unless of course, they are a pyromaniac Sim.
Seeing a ghost also should not make a Sim tense, it should make them scared...unless they are curious about Ghosts. Scared could have 3 levels...Startled, Frightened, and Petrified. Going up behind a Sim, successfully sneaking up on them, and yelling "Boo!" might result in a Startled mood. Witnessing supernatural power could result in Startled mood, or witnessing evil magic or a Vampire feeding could result in a Frightened mood.

Seeing a critter that doesn't belong there might result in a Startled mood, such as seeing vermin in an apartment, which would then degrade to a Disgusted mood over time. Disgusted should be a mood of its own too: Disgusted, Grossed Out, and Nauseated could be from least to most. Squeamish Sims or Neat Sims could be more prone to being disgusted, and Sloppy Sims less prone to being disgusted. Witnessing a vampire feeding or zombie feeding could also result in a disgusted mood. Reading troll post on a forum could also result in a disgusted mood (all the Sims can "troll teh forums"....but who reads them?)