I think many of these were hinted at in the story to be honest.
There seems to be a difference between trying to get closer to Wonder of U and trying to actually reach him. This is how Wonder of U can invite people to his lecture without hurting them, and how the reporter could get within talking distance. Threatening to expose him to the world wasn't pursuit so Wonder of U threw some bullshit at the guy to re-contextualize the action as pursuit in his mind in order to get him hit with calamity.
Jobin got killed because he saw Tooru, not because he tried attacking the stand. If you're being attacked by the stand, seeing Tooru gets you killed imminently. Tooru explicitly points this out as the reason he's hiding, in the hopes that Yasuho takes the chance to leave and live a happy life.
Wonder of U apparently gets less dangerous the more injured Tooru is. The first injury Tooru took was a complete fluke and after that Josuke was able to get closer to Wonder of U than before. The second time, the plane door veered off course last minute. By the third time, he was so badly injured that Caato could approach. I think Caato was wrong about "this doesn't count" though, as the specter of Wonder of U did appear on the scene immediately. It's just that it was too badly hurt to kill her before she killed Tooru.
I'm pretty sure WoU mentioned that part of the elevator plan was to give people an opportunity to follow it further and get more injured by that rock bug.
Wonder of U is explicitly a karmic mechanism so bad people are more at risk than good people. Poor Tom and Jobin are both kinda assholes so they were hit much harder than the Jobros. Also look at Dolomite when they interrogate him. That guy was shitting his pants at the thought of having to talk about who the Rock Humans work for, and then when he realized they meant Jobin he was relieved.
Seeing the "image" of the stand, at all, causes calamity. Image seems to be distinct from the actual body, as it looks like it exists in multiple places at a time and the images only appear near people who tried to pursue it already.