[13lackGu4rd]

1. going AI is bad. only exception would be if you've lost your capital and all other forts and can no longer recruit anything and are just waiting for others to finish you off. even than I'd just stick until the end(like I'm currently doing in 1 game) as the turns no longer take time, and going AI is just bad. other than the exception, you're describing a playable situation, whether you think you have a chance or not at this stage is completely irrelevant. you should keep on playing because you're not dead yet and you can still play. if you feel that you're just playing too poorly and believe you can't win because of that than finding a sub(a more experienced player than yourself) to carry on instead of yourself, is an acceptable course of action(as long as the game is not a "newbie only" or something).

2. I really don't understand this example. I assume "whatever reason" is binding diplomatic agreements, otherwise territorial exchange would change the picture and open possibilities for nations A and B to wage war against each other. even than, with spells like teleport, cloud trapeze, gateway, etc, sneaky troops and commanders, flying troops and commanders, etc I don't see how giving up a province or 2 will "funnel" a nation to go into a "kill zone". generally giving up territory without a fight is a bad deal, unless you're cooperating with the nation you're freely giving up territory too, and you do it so said nation can help you against this common enemy.

3. as for playing Kingmaker or not. there is no simple answer here. on the 1 hand you can go with the "do not interfere" philosophy if you feel that no matter what you do, you can no longer win yourself, however your interference towards 1 of the sides will severely change the balance of the game. on the other hand you should look at the game's history, previous diplomatic actions by both sides, were you in a war with any of the sides before, did any of them block you from achieving your goals, etc. this way you can decide which side you prefer to win, and help them. you can also use personal preferences, say if you like player A more than player B, etc. sure, it may be frowned upon for the sake of game balance, but it's only natural that people tend to support their friends over strangers...