How to wire a C/B into a dual battery set up

[FGT]

QUESTION: How to wire the C/B into this current dual battery set up.

EXISTING SITUATION: MAIN Battery is OEM and feeds OEM circuits. Added an AUX Battery in the OEM dual battery location. Connected the AUX - terminal to the MAIN - terminal. Connected the 100A Accessory Fuse Block power cable to the AUX + terminal. Installed a smart isolator between AUX and MAIN batteries where a cable from AUX + goes to the isolator and a cable from isolator to MAIN battery + terminal. Installed separate QD battery tender cables to both AUX and MAIN batteries + and -. The dual battery system appears to work as intended. For this Phase 1 improvement, to avoid having to constantly pull the leads on the AUX + battery post off and put on, for testing or maintenance of Accessory circuits, I wanted a more convenient and safer way to open the circuit from the AUX battery + terminal the Accessory Fuse Block. I called an off road dealership and was told to install a much larger capacity circuit breaker than the 100A rated Fuse Block and was recommended to get a 250A C/B like the one in the pic, which I did. I was told the reason for the C/B high amp rating was two-fold (a) to trip in the event of a battery short circuit and (b) to be able to conveniently open the C/B to kill power to the Accessory Fuse Block without removing leads from the AUX + terminal. The 250A C/B has two posts labelled "BAT LOAD" and "BAT LINE". There are currently three connections to the AUX + post: (1) Accessory Fuse Block power cable, (2) cable to Isolator AUX in terminal, (3) cable from AUX battery charger.

[FGT]

Received guidance from a logical soul on the Kawie Riders forum: Acc Fuse Block Power to BAT LOAD, install new cable from BAT LINE to AUX + (and) leave the other two (Battery Charger + and Bat + to Isolator connected to the AUX + terminal since neither are loads.