"Truncated ELF file" => standard OS commands are unreadable.
Leave the disk as is.
Salvage config.xml
Reboot using a install device and install from scratch.
When you are asked to format the destination drive, do no go for quick one, but chose the non-default total format with check (I didn't re install pfSense on a physical disk, mine just wont die after nearly 10 years ...)