Carl, having served in a couple of different regions in Iraq, and having been in all, the dynamics of the conflict(s) are different in each, so I don't think even someone who is a so called expert on Iraq can answer your questions with more than educated speculation.

1. Did AQI and the Iraqi Islamic Extremists grow in power to the extent they
displaced the FRLs as the driving force in the insurgency?
This is a great question, but it is also possible that the FRLs are funding any Sunni group that is anti-coalition. While they may fight one another in the future, or even fight one another now, I wonder is FRLs expats are funding AQI?

2. Are the "tribal revolts" against more than AQI, are they also against parts of the FRL insurgency?
I have seen tribal revolts against JAM also (a Shi'a militia group).

3. Are the FRLs still the relatively cohesive group Malcolm describes in his
book?
4. Have the FRLs, or some of them, given up pursuing the insurgency? If so, for how long and why?
I don't know, but I wonder is the FRLs see the Shi'a as a greater threat to their objectives than the coalition forces?