I'm going to try my had at being an unimaginative pragmatist here, so bear with me.
Take that long list of yours and toss it out, nothing is going to be as effective as lowering the "A" in the CdA formula.
As with any type of pickup truck cover, you have already compromised the utility of the vehicle, frequent large heavy loads are not a daily routine to say the least, right?
Lowering the truck depletes it of most it's cargo holding capacity, but it is the simplest route in my opinion.
Below is a truck I've seen recently, I forgot to ask him about his MPG, we talked mostly about Eastwood rust preventive products having a marginal effect.
2016 Misc by George Kachadoorian | Photobucket
Just food for thought.
I'm sure the baby moons and tiny sport mirrors help a bit.
Perhaps go one step further and seal off the gap between the cab and bed?