Neat project, and definitely not cheapening out on the products.
The one photo looking down at the 500 amp Deltec shunt and fuse, it looks like the 4/0 lugs might have 'ears' on the crimps below the thick wall adhesive heatshrink. How are you crimping these?
I keep wanting to gain experience with Lifepo4, but have mastered the care and feeding of TPPL AGM's, and will wait on the fence for a few more years at least.
To fellow readers, this article can show how far that proper wire termination can be taken, and one photo showing crimp ears:
https://marinehowto.com/making-your-own-battery-cables/
https://marinehowto.com/marine-wire-termination/
I unfortunately own the HF hydraulic crimper he tests at the end of the first link, and they are as bad as he says. I've ground out some of the Dies for 2awg thick walled ring terminals, as the biggest dies labelled 0awg, only do 4awg somewhat adequately.
Its a very clunky tool, but I have achieved quality results, taking abut 10 times longer than a proper tool would to achieve a better result.