On (1.)...
There's a pretty fair chance of war happening so long as the thief is the human player, but nonetheless this is not the solution you're after.
It's a bit disappointing that you've got to the finish (Ottock?
) of your scenario authoring, as the method I propose will require quite a bit of restructuring if you want to give it a shot.
You will need to create a separate technology tree for the protagonist tribe, or at least one that contains a different tech' tree 'to be researched' from the game's commencement than the other tribes.
You will also have to prevent negotiations between the protagonist and the other tribes to avoid technology exchanges (and to a lesser extent turn off 'tech by conquest') also for it to work in its purist form.
Then fill your events file with...
If received technology... technology = (advances researched by other tribes)... then make aggression... who = (all tribes will need to be named)... whom = protagonist tribe.
The result of this (apart from a very full events file) will be that every time the protagonist acquires an advance that they cannot research, trade, or access by conquest (i.e. they must thieve to get it), all other tribes declare war on the protagonist. The problem being that the event structure does not indicate from which tribe the technology was stolen, so in light of lack of other options, have every tribe declare war.
It will require a fair amount of messing around, and as before, will take up a fair chunk of your events file, as you will need to make a separate event for each tribe and each technology.
On top of that, certain technology slots have special effects on the game, so these too must be borne in mind when setting up such a system. I refer to you the Scenario League's Design Tips for advice on special advance slots and building divergent tech' trees if you are unfamiliar with these matters.
Perhaps someone else might have another suggestion?
As for (2.)... errr...
