"I also put a 15a fuse each, in the switched power source wire, and the wire that goes to the middle of the factory starter relay (with the square retainer on it, don’t know what it’s called)."
WHY, on the ford relay? It's only on when you crank the engine, totally unnecessary. Okay, but it's there now.
The trigger wire to the CD relay is OK to have a fuse in it. :thumbsup:
Cable from the left side of your ford starter relay to the cutoff switch in your tail panel is the one that needs a breaker or fuse. That is the one that I suggested the breaker be installed on,
NOT the cable from the alternator, although you can certainly fuse it if you like.
I forgot you suggested that. If I remove that breaker from the alt. cable, (this one)
https://www.amazon.com/gp/product/B08RX5QN4P/?tag=fabo03-20 can I use it (is it the correct one) between the left side Ford solenoid and the cut off switch? You mentioned a rating being different because of the 12-48 volt rating of the breaker. I don't understand the theory there. I get that the 1/0 gauge from the Ford solenoid to the cutoff, and from the cutoff to the factory starter solenoid (now a bus), is too heavy (you did mention that). I'd like to replace that with something more appropriate. Would 6 ga. be adequate? I believe 10 ga. is factory, with a much shorter run.(Again, I don't know how to figure that.) I had been thinking that starter amperage went through that, thus the 1/0. It would also be easier to connect a lighter wire to a lug that would connect to the breaker, instead of 1/0 ga. to a relatively smaller breaker. (At least as far as my limited knowledge goes.)
Your starter relay up front is ONLY a buspoint. Look at the SCHEMATIC!!!! That 1/0 off your cutoff switch does NOTHING regarding the starter. NOTHING! Power for the starter is provided from cable on the right side of ford relay. I usually run a maxi fuse that pops at 40-60 amps on a 12v system on that line depending on expected loads.