Thanks to a super helpful tip from @DosFox, I now know that the sunrem 2MB card needs SIMMs in slots 1 and 4 to have 1MB, and not 1 and 2 as I originally had them.
The current process right now is:
on first boot memory test will pass, but IO fail with error 57. I can't boot to floppy
soft reset makes it pass all tests and let's it boot from floppy