Wtf... could it be this simple? You say the A1_V_VivecInformants line isn't working? Could this be because it might be missing a comma? I just noticed this. Most journal commands at least are in the form Journal
, "Quest ID", value. So try once more writing:
Journal, "A1_V_VivecInformants", 50
.
If this works, we should edit the UESPWiki since clearly there would be a typo.
I see another problem possibly yet coming if you have saved the game after the erronious console commands. Since the PCRaiseRank command has always worked, you might have raised your Blades rank many times trying to make this quest work. Right mouse click to open your inventory and other menus and see from the bottom of the upper left-hand-side menu (default) if you still are an Apprentice with the Blades as you should be at this stage. If you are higher, put in the command
PCLowerRank "blades"
as many times as you have to. http://www.uesp.net/wiki/Morrowind:Blades#Blades_Ranks are the possible ranks. So if you've become e.g. an Agent, activate the PCLowerRank five times before talking to Caius and finally moving on from this surely irritating problem.