Last part first: When I want to capture the whole sound of my guitar amp and cabinet, I will plug the guitar into the amp and use microphones plugged into the FireFace to record.  I've used the classic technique (Shure SM57 right in front of the best speaker) but I prefer to use a large-diaphragm condenser mike several feet away.  If I'm using digital effects, I'll plug the guitar into the FireFace instrument input (#1) and then use the H8000 and DAW to process the sound.  I'll usually record the guitar without any effects or processing on one track, and the effected sound on another track.  I will also run the guitar amp like an effects loop from the FireFace: guitar in to the FF; out the FF to the amp instrument input (through an impedance-matching box); out the amp preamp output; back to another FF input.  This gives me real tube-amp distortion.