The Fireface 800 provides 2 additional ADAT inputs so you can add up to two OctaMic II to the setup which will give you up to 20 MicPres. For up to 16 additional analog outputs you need two ADAT converters like the RME ADI-8 DS or ADI-8 QS (high-end, but more expensive). Or go for the M-16 DA with 16 high-end DA outputs.

Yes. TotalMix works like a complete digital hardware mixer with all I/Os of the Fireface connected to it - including software playback channels from your sequencer(s). With the unlimited routing and mixing options - unlike any other hardware mixer on earth - every physical output can work as own submix or aux bus. You know a classic mixer has 4 or 8 aux sends, which could be used for headphone or FX mixes. In TotalMix every output can work as aux or submix bus and could get a signal from any input or playback channel.

Yes. TotalMix is your desk with total flexibility (see above). You only have to use a physical output (like SPDIF out) as FX bus and build your reverb mix there. Connect this output to the input of your reverb processor. Route the wet signal from the reverb to an input (like SPDIF in) and route/mix it to your main monitoring and headphone outputs for different reverb mixes.

best regards
Knut

If you connect one OctaMic II to one ADAT in of the FF800 you still have two ADAT outs (16 channels) free for two ADI-8 DS/QS or one M-16 DA. The OctaMic II is only an input device and needs one ADAT input (and maybe an ADAT output of the FF800 for the clock).

best regards
Knut

Just one more question. Is there any way to insert a hardware compressor or any other outboard before the converters?  Thx, NLee