There are guys on this forum far more qualified technically than I am (Bawareca could you offer any insight) but I would guess you're looking at an electronic fault. Possibly no comms to one (or more) of your modules?
I have had a transfer case control module go bad on me and the the error code was similar to the first one you listed..of course my vehicle still ran fine, albeit without ABS, DTC, EBD or 4x4.
Since you've only ever known the vehicle in a state of disrepair is it possible some of the electronics have been scavenged prior to you taking over ownership? Do you have a full history of the vehicle? ;is what I'm getting at.
It may also be something as innocent as a harness that is unplugged. Perhaps you've forgotten to reconnect something?