For (1), I've not been able to do this with MIR Plug-In, but I have been able to do it by using MIR inside VE Regular.
There is no straight-forward way to do this with MIR Pro's plug-in version, due to restrictions of the routing concepts of most (if not all) DAWs - sorry to say so. Activating the preference to force the number of Output Channels to a certain value won't help. Only VE and VE Pro offer the necessary special solutions when hosting MIR Pro in its native version.
Kind regards,
/Dietz - Vienna Symphonic Library