There is a lot of questions there. Mostly answered by searching a few of the 6910 threads.
I will go into your final query regarding brew temperatures...
In the manual, it describes a combination of buttons presses to move the brew temperature -10°, -5°, 0°, +5°, and +10°. I'm not sure of the set temp, but mine seems to be about 85° into a pre warmed cup (I'm working on more accurately measuring this).
It is controlled by a 100k ohm NTC thermistor that talks to the control board to switch the group head thermoblock on and off.