I know you've been inundated with instructions so sorry if I'm repeating stuff you have tried but here goes:
The controller should be set to transmit MIDI on OMNI, ( read manual )
If using MIDI use keyboards MIDI OUT and run to the MOTO midi IN
You should now see action in the MIDI icon down in the tray.
The MIDI track input set to either your interfaces MIDI input ( MOTU Midi in) or the keyboard ( Roland A 800 ) if it uses USB.
Set the input channel to OMNI to rule out channel assignment being issue)
Load Session Drummer go the the GUI and load a drum kit into it, test output with mouse.
Put focus on the MIDI track, Turn on input echo, set output to Session drummer
and it should now respond.