to 1) yes, connect the XTC to the 802 using one or two ADAT TOSLINK cables.
If you want to route only the 8 Micro Pres @44.1/48 then you need only one TOSLINK cable.
If you want to route more than 8 channels or the Micro Pres @88.2/96 or even higher, then use two TOSLINK cables.
Keep in mind, that one ADAT port can only support 8 channels @44.1/48 kHz.
If you double or quadrupel the Sample frequency, then multiplexing of several 44.1/48 channels takes place, so that you will end up with only 4 ports @96 or 2 ports @192 over one ADAT cable.
to 2) connect MIDI cables between XTC and 802 (2) for remote controlling the XTC through TotalMix of the 802, which is connected to your Mac.
to 3) no, has been asked already in this forum
FYI .. XTC manual has been updated today to version 1.3 and contains the setup to remote control XTCs from UFX+ using Midi over Madi. Part of this information is useful for you how to do this by using 802 and Midi.
FYI 2 .. there is an application available called Midi Remote, which makes it possible to remote control an XTC fully from a Windows PC or Mac. Advantage, you can perform complete configuration using this application. But it can not run in parallel with the Remote Control via TotalMix FX. I think remote control via TotalMix (to configure/use the XTC as so called "Aux Device") has more advantages for you, as then you can save Gain and other parameters together with TotalMix Snapshots and Workspaces.
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14