Your California stats are misleading. First, you said that drugs are responsible for the "majority" of our prison ills, but your chart shows that 77% of people sentenced for a second or third strike are for property or personal crimes, or gun possession.
Second, California is unusual in that the third strike can be anything (first two must be violent felonies). So people are in for drug possession, but also for other minor things like larceny. In most states, drug possession doesn't trigger the three strikes rule at all.
In any case, three strikes rules weren't created because of the drug war, even in California. It was a response to a guy who murdered a girl. And note that in several states, these rules passed by public referendum with huge margins less than 25 years ago.
No, not since the passage of Proposition 36 in 2012: https://en.m.wikipedia.org/wiki/Three-strikes_law (see "California")
But fundamentally the three strikes rule is a bigger issue there than the drug possession charges themselves, the three strikes remove all judicial flexibility and agency.
http://www.people-press.org/2014/04/02/americas-new-drug-pol...
As for three strikes, drug possession was one of the top offenses for which it is applied.
http://www.lao.ca.gov/2005/3_strikes/3_strikes_102005.htm
"Possession of controlled substances alone made up 12 percent of the state’s [CA] total three strikes population at the time — drug crimes in general accounted for 23 percent."
http://m.huffpost.com/us/entry/three-strikes-law-drug-addict...