I really have no idea if the red dip is plausible or not, I simply don't know enough atmospheric physics. In fact, I hardly know any atmospheric physics at all.

As for the motives and planning of potentially suicidal nuclear-armed martyr/fanatics, I'd say all bets are off. All wars tend to turn out very differently than the participants anticipate when they start. Only WWII turned out roughly as expected, and that was only for the side that won. Both the US and the USSR understood this very well.

Regarding your third statement, that is a classic case of apples and oranges. Wars can start by accident, or just because the two sides lose control of the situation even though neither really wants war or even thinks it can happen. Ever read "The Guns of August"?