As for the various grim fates that befall most Psykers, I would treat such information as being potentially subversive, and thus Forbidden Lore.
Hmmm... probably. I'd also like to think that due to the negative propaganda-campaigns the Imperium (especially the ecclesiarchy) runs against psykers (burn the witch, abhor the witch etc etc) most people are actually glad the psykers are being carried out of their sight... Common Lore: Psykers would probably also include the awareness of there being Psykers who are not witches-to-be-burned, thus unless you have a person of authority with you (or at least act the way you are the PoA) it'd soon result in a witch-hunt or everyone simply running from the witch, should they be too open about that.
Another way to keep spammy psykers in check (say that five times very fast!), which has doubtlessly been used quite often though
On the other hand, I'd probably also add the CL to some point in the career of the Arbitrator (as they have to know about the mark of sanctioning) and the Imperial Guardsmen (Probably the Sergeant-Path, as psykers are relatively frequently used in the Imperial Guard/Astra Militarum)