I am curious where in the schematic is (in the picture above) what looks like junction connector with three wires going to it in the upper left of this picture, it is not part of the starter or solenoid and is insulated from ground.
Upper
RIGHT is 6A from the battery (thickest wire), 81A (the next thicker) and 81B. This is battery hot (+).
Upper
LEFT is 74A and 74B. (there are only two wires here). The wire on the
SIDE of the starter (where 74 goes) is on the starter/solenoid itself and not part of the vehicle harness.
Lower
MIDDLE is 7A and 30. This is the vehicle ground. (As I said, the third red wire is just an additional ground that goes to the engine block on my rig.)
6A - Battery Positive (directly to the battery)
81A - Goes to the EESS box (+)
74A - Goes to the EESS box (start)
7A - Goes to the battery Shunt which goes to the battery negative (-)
74B - This goes to the STE harness connector 'S' for diagnostics.
30 - This goes to the STE harness connection 'M' for diagnostics.
81B - This goes to the STE harness connection 'T' for diagnostics.
I know there is a way to kick in the starter from the STE connector, if I had to guess it would be connection 74 (S) and 81B (T). But I've never tried this, so I wouldn't suggest it without you verifying it.