Dalinar might mention it in private to Jasnah, we know he trusts her and he might figure that Jasnah's one of the best people to talk some sense into Elhokar, or Dalinar might mention it to Navani, and Navani might mention it to Jasnah.
I don't think Taravangian would deliberately put Szeth on the same boat as Shallan and Jasnah, because if they saw him on the boat and then during the assassination and the didn't get killed i the process they'd know to trace him back to Khaarbanath(sp) and Taravangian won't want to risk anybody having any chance of tracing the assassination plot to anywhere near him.
There's definitely going to be a reckoning between Kaladin and Amaram sooner or later, and if you're right about who Kaladin killed and Shallan finds out that Kaladin killed him there's likely to be an awkward scene between Kaladin and Shallan eventually. I hope she'd have the sense not to be really mad at him, but still awkward.