If you double checked the ground wires with no success - is this a standard transmission? If so, have you checked the clutch switch? This wouldn't explain the stalling and no start issues, but they may be separate issues. Actually that seems highly unlikely now that I typed it.

You mentioned professionally soldered, did you just have the pins on the edge (the common spot) re-soldered or did they go over the entire board? Possibly a faulty relay on the RCM? I am sure someone will correct me if I am wrong, but I would make sure the relay was energizing prior to any other testing.

Ryan