First up, I'm unwilling to read 16 pages of thread. So if what I say has been said/done/discounted, you'll get over it
Assuming you have access to engine and trans control:
Engine:
Make sure you have some kind of deceleration injector cutoff, and make sure it's agressive (say, 1100rpm cutoff point).
If the trans control and engine ecu are linked, see if you can run torque reduction on shifting. This will allow faster, smoother shifts that will wear the clutches a lot less.
While you're reprogramming your engine, try find out if better atomising injectors will fit. Some people have noted economy gains going from changing to a more modern injector that had the same flow rate thanks to improved vaporisation
Trans programming:
Lock the torque converter as often and early as possible, even in first gear. This may require valve body modifications as some transmissions only supply pressure to the solenoid in higher gears to avoid stalling in case of solenoid failure. You'll be maintaining your gearbox and are probable handy enough to replace a solenoid anyway. Wire in some kind of switch (or use the power/economy switch dual map function) to allow factory style torque converter use and shift points for when you are towing.
Select the highest gear you can for the power required. This will likely be shifting earlier than the factory points.
Select the highest gear *that will activate the injector cut* under zero load. This should allow you to back off from highway speeds and coast for a long time, with the torque converter locked and only downshifting as the engine gets to almost idle, only using fuel when you get to about walking pace. This has the effect of minimising engine braking automatically, while not using fuel.
The net effect of these mods is to increase your transmission efficiency to be close to a manual transmission under most circumstances, with automatically perfect shifting for economy. You'll never get the same economy as a *perfect* manual driver while the gearbox is pumping so much oil around, but the always-perfect shifting and ever-locked torque converter will get you close *all* the time.