"could shuttle 1 make an unmanned return to earth, and if it doesn't suffer significant re-entry damage, to auto land?"

The shuttle was never designed to fly itself, which is why the shuttle's first orbital test flight (STS-1) had a crew.

After the Colombia accident, when NASA developed the rescue mission plans, they made a cable to link the onboard general-purpose computers with the avionics systems on the flight deck to allow the shuttle to attempt to fly itself back. The cable was launched and stored on the ISS during the return to flight mission, and was brought back so it could go up with atlantis on this flight.

Funny thing is, the russian Buran shuttle was capable of flying itself and the only orbital flight it made was uncrewed since at the time, there was no life support and most of the avionics instrumentation wasn't yet installed.