What does the single wire off the 1 wire alternator do? It charges the battery and runs the car. I have no idea why you would think that is a field wire... a 1 wire doesn't have a field wire.
The main alt charge cable runs to where you have that yellow wire. You use ALL the OEM stuff up front, EXCEPT the OEM black charge wire that hooks to alternator. That black wire powers the car and you need it disconnected to isolate the alternator and battery from the other side of the cut off switch.
Follow the schematic EXACTLY, it works.
You see my picture. The black wire from cd going to right is power to the cut off. The other black wire going forward hits the starter relay. That is the ONLY wires attached at the cutoff switch. I also have a 60 amp maxi fuse in line to the cutoff. No alternator or starter cables.