Backstabbing is just a sign of different gaming culture... Certainly not on par with actual cheating, which using the masterpassword to one's advantage would be! Verbal abusiveness is another matter again; although very loutish, it isn't cheating either, and should be handled the usual, social way.
With the master password one open any players turn files and do the same things the player could. I'm willing to trust a personal friend of one of the players with it; indeed, consider the alternative, some screen name whom no one knows!
To comment on backstabbing some more, consider this: If the game's goal is perceived as giving one's best within the limits set be the rules, and the joy in the game is derived from performing well, backstabbing comes naturally: Indeed, at some point of the game, one might consider a player who _doesn't_ backstab a clear winner to play poorly and to ruin the game for others. (If you know the classic board game, Diplomacy, please compare!) Well, I could go into detail, but suffice to say that as long as it's within the limits of the rules (both overt and "hidden") it's ok with me. Some might consider it poor tact to do some things, whilst others see them as necessities to satisfy the collective need to do one's best.
I wouldn't want such a trifle as getting a sub to sour the mood, though, so please rex, check the graphs and see that Ulm can't touch you
Oh, and the AI is pretty straightforward to deal with as Ermor; it doesn't often dare to attack against your massive hordes, so just put a couple hundred dudes on your borders and attack at your leisure.
Pan mages are not that hot against your horde, and vineogres can't hold out against superior numbers; you could consider just swarming the ogres and flanking his mages with cavalry; vineogres dissolve when all mages are dead IIRC.