I didn't go back and look, but did you do a voltage drop test on your main cables, including ground?
Run it, warm it up, and start at positive wire to alt, pos to starter relay, ground wire to engine, etc
All you need is a bolt meter. Lots of vids on how to do it on YouTube.
Once you test those as ok, test from starter relay to bulkhead, working your way inside the car ( while running)
Your basically looking for voltage that's "locked up" in the wire due to corrosion, dirty connection etc. Corrosion can work it way inside multi strand cable, and you can't see it
I know swapping parts SEEMS easier/quicker, but it's really not
Here's the basics
https://axleaddict.com/auto-repair/Automotive-Voltage-Drop-Testing
In the real world, your probably gonna see .5 volts alot, your looking for a bigger drop that that