Make the sdcard a read only root fs, problem solved
Yeah that's more or less my goal for the setup in the post... I didn't have much time to investigate what else I could move off of the SD card but I suspect there's a few other things I could do. NixOS makes it super easy too.
Doesn't actually help. It eventually goes corrupt anyway. It might be related to power ripple or something.
Makes it easy to replace, though.