Hi Pixelpoet,
I can't answer all your questions with authority, because although I'm the guy who comes up with the MIR Pro settings for the VSL's "Synchronized" series, I'm not the one who actually implements them into Synchron Player.
ad 1: The settings you see in Synchron Player are derived from the individual wet/dry ratios exported from MIR Pro which is treated as "new zero" there.
ad 2: All IR exports are made with the same reverb length in MIR Pro, which is again treated as "new zero" in Synchron Player (AFAIK).
ad 3: All exports are made with exactly the same mic setup chosen in MIR Pro (which differs vastly from the multi-mic array used for the actual Synchron Series due to the Ambisonics format used troughout MIR Pro - but that's a different story altogether. :-) ...)
HTH,
/Dietz - Vienna Symphonic Library