When you boot with no startup-sequence from early startup screen & once @ the cmd prompt, ....if you type:
"Assign Env: Ram:" - Return <--- this is Enter Key....
"Assign T: Ram:" - Return
"Assign Clipboards: Ram:" - Return
"loadwb" - Return
....you won't be prompted to insert volume Env: ....because you make the assign the Workbench startup-sequence calls for when executing itself.
I can't help with the error codes, but in layman's terms & forgetting them for a moment, search your thoughts based on what you already know....
Strip the A4KD & re-build her card by card & see where it falls over. You might fall over before putting cards in, meaning the SCSI Hard drive is/could be suspect. If the Miggy is fine with an extra hard drive in it when booting from said drive, (IDE) then the SCSI drive has to be dying one way or another.