Upgrading my '04 Minnie

[Desmonic]

So ... I bought an Iota DLS-45 after my stock converter / charger cooked my batteries. Also bought a 200ah LiFePo4 battery and a Redarc BCDC 1240D to control the alternator charging of my new battery.
Then I went to install the Iota. NOT a direct replacement.
Then I investigated the stock alternator charging system. The cable departs the battery, goes to the starter, then heads back to the battery box where it attaches to a solenoid ...
I'm over my head.
I contacted Redarc three days ago for direction (can I use the stock cable that routes through the starter or should I run a new one? Do I lose the hot start button or can I wire around it?). Haven't heard back from them.
Should I do away with the factory remote battery isolator switch and just wire in a heavy duty cutoff switch (Blue Sea)?
I moved the battery and all related stuff from an exterior compartment to under one of the dinette seats since LiFePo4 batteries can't be charged below freezing.
'04 Minnie 322E.
HELP!