PeaceWeight determines the attitude of the AI-Leaders towards each other (not towards the human).
It is set for each leader at the beginning of each new game as it is slightly variable: PeaceWeight = iBasePeaceWeight + random(iPeaceWeightRand)
iPeaceWeightRand = 3 for all leaders and iBasePeaceWeight is 0 for Monty ... 10 for Gandhi.
so Monty gets a PeaceWeight between 0 and 2 whereas Gandhi's will be between 10 and 12.
Then change in attitude = +4 - absolute value of difference in PeaceWeights, so
Monty-Gandhi: -8 .. -4 (they hate each other)
Monty-Genghis: +2 .. +4 (they like each other)
Warmongers will like each other even more due to iWarmongerRespect.
Those are "hidden" changes which you will not see directly in the diplomacy glance screen. But you will notice that Monty might be furious towards Gandhi although the screen displays an attitude value of -4.
I'm not really sure about iMaxWarRand, there are so many factors that influence AIs' war plans...