Question one: In my first playthrough I worked through a number of trades and treaties trying to improve my relations with other kingdoms, but nothing seemed to make a difference except for the pluses and minuses on the right side of the foreign relations screen.  This second playthrough, all I did was attempt to stay very powerful so I could cow everyone else into liking me, and that worked perfectly.  But I've also seen forum posts where people talk about actively attempting to maintain good relations with other kingdoms, even weaker ones.  Am I missing some aspect of this, or are they wasting their energy?

The second question is perhaps more theoretical:  I read a forum post someone wrote about their diplomatic victory, wherein they allied with a weaker rival, took out the third kingdom, and the game was over.  That makes sense in relation to the description of a diplomatic victory.  But it occurred to me, if the other kingdom is stronger (in game terms, we'll say their faction power is greater), wouldn't you logically be handing them the victory?  I can't imagine that's what actually happens in such a situation, but it would be fitting if it did.  Or, since everyone would scream, you should at least have to continue playing to beat down the other kingdom.