It's a little bit confusing, both parties determine EndWarValues and they represent their benefit of not continuing the war.
I.e. if a weak player is under a lot of pressure and his cities are threatened plus his powerful opponent was able to accumulate a lot of war success, then this player will calculate a very large EndWarValue. On the other hand the strong unthreatened player will determine a very low EndWarValue.
During peace negotiations both teams put their determined EndWarValues in the balance --
but on the opposite side of the balance! Thus the weak player needs to add other stuff (techs, gold, cities, ...) on his side to achieve a 'fair' balanced trade.
Therefore our goal is to lower our EndWarValue and increase Toku's EndWarValue as much as possible so that he has space to add techs on his side for compensation.
If we endanger more cities than Toku, our EndWarValue gets reduced via the presented division by 3. We should further avoid any war success for him. Even though Toku clearly has the higher power this division and our better war success so far will lead to a difference of the EndWarValues that should allow us to get Archery from him.
In addition to this reduction of our EndWarValue, there is also the dubious doubling of Toku's EndWarValue I mentioned for the case that Toku started a
total war. AFAIK we can't tell whether that is true or whether he chose a
limited war, but if it is true we might even get about 3/4 of Math from him (rough estimate!) -> we need ~100

invested in Math, less if Hammu gets Math too (e.g. in a trade from Toku for IW).