Knossos 0.13.3 fixed the bug you encountered in 0.13.2 so it's safe to update to that. It most likely won't resolve this specific issue, though.
Can you try and go to Knossos' settings, select Nightly as the preferred stability in the Knossos section, save, update FSO and launch the mod again? It will most likely crash with the same error but I'm hoping the conversion to JSON will work regardless. If it worked, you'll find a file under %AppData%\HardLightProductions\FreeSpaceOpen\data\players\<PILOTNAME>.json. Please attach that file to your post (if it exists).
If that didn't work and you still can't launch FSO, you could try cloning your pilot but aside from that IIRC the only solution is deleting your pilot.