Hi there Kev,
I've done all the mods you intend doing.
I've the Synergy2a set on 8 for max torque and medium power.
That's with the Pierburg MAF of course - if you stay with the original Bosch MAF then the equivalent setting will be number 3.
According to Ron's info, which I agree with, the extra power settings would only help with more HP at over 3000rpm - so that for towing is a waste of time.
I tow a big non-aerodynamic trailer with my auto-box 2004 Freelander which has now done 112K miles with no problem. Usually loaded to around 1600kg although the trailer is plated at 2tonne max gross.
I should really fit a roof-spoiler as it's the wind resistance more than the weight that I feel.
Running legal at 60mph I can get 26 or 27mpg - but long hills a bu**er. For example on the M6 from junctions 35 or 36 heading north to Carlisle I let the speed drop to around 55 and can make steady progress - even passing caravans with lesser capable towing vehicles.
Without the trailer I get over 36mpg - even fully loaded with a roof box. With just 2 people on board and no roof box I can easily achieve over 40mpg.
My present auto with a synergy gives more mpg than my previous manual did without a synergy.
I keep the auto-box in normal drive - not sport mode - otherwise the box hangs on to lower gears much too long for me.
Hope that helps you.