Well, after taking a long time away from the boards I have an update for those mac users out there... ;D
Same mac setup as posted originally, but with the OS v10.13.3 (17D46a) High Sierra BetaOS. It seems to work fine without dropping the DAC in USB, but the best/smoothest setup that works is the S/P Dif interface through a schitt converter (EITR). No problems and I can't honestly tell a difference between interfaces- TOS, USB, or S/P. I think the MIDI interface software by Apple deserves a workover, but I just test and play with this stuff. Whatever power management that Apple OS went through seems to be worked out without doing anything on my part but waiting... Using Amarra Luxe as well.