Without parallel programming,
AND if the PSEN boot does not work,
you can try to make an eeprom,
use EA Low to run from eeprom,
and run program to fix boot vector.

If this isn't enough, you can try executing chip erase, your own IAP, etc. in the external eeprom.

This might make more sense than trying the parallel program method.

This might not work if security byte programmed, but you seem more concerned about the boot vector and status byte.