Thank you for reading through and for your feedback! Excited to try your settings to disable the WAL and other overhead and see if I get even faster inserts.

Also glad to hear an expert say that WAL data isn't really necessary for bulk loading, especially with chunks. I should get through the ~20 days it takes to load data without a power outage haha (no UPS yet :() but it sounds like even in the worst case I can just resume.