Again going from memory
Only 2 books came out in between the 2, Geralds Game and Delorous Claiborne, both of which have very heavy "entrapment" style themes, which very well could have been an "Exorcising the demons" kind of deal. I don't see it as "schizophrenic" so much as a massive lifestyle change at the time.
As to the editor, he has pretty much kept the same ones for long stretches IIRC as well.
Yes, but that is sorta the point.
His best work was IMHO when he WAS "on the drugs", the subject matter really lends itself to the scene, and quitting may have given him the literary equivalent to bad Acid flashbacks