The unexpected file format error typically means that one or more of your data files has been corrupted
If that's true, then there is no change of saving the corrupt files. (I do hope you have backups)
Changes are that not all data files have been corrupted.
I would suggest that you make a new project and then copy 1 file at a time from the data folder of your corrupted project to the new one and then run the project.
That way you can find which files are corrupted.
*hugs*
- Zeriab