1. Disaffiliation doesn't happen equally across Christianity. Mainline Protestants are shrinking because older members aren't being replaced by their grandchildren. Catholics leave because they're disgusted by clerical abuse.
4. Conservatism/intolerance alone doesn't explain evangelical attachment to the GOP. I have long believed it's that they share a high respect for authority. That's not the same as authoritarianism - I don't want to tag anyone as a fascist.