What code language does IVAN saves use?

Im trying to fix my save with an error message of "Player can't be found anywhere!", and when i try to look into the code it just shows rubbish. i have many backups but i believe all of them are broken since using them results in the same error.

I don't know for certain, but the savefiles are just a whole lot of data smooshed into a file.
We probably need a utility to be able to unroll the data into a table and be able to make repairs, but I don't know how much work that would be. Probably a lot.

Anyone been able to look inside a savefile yet?

Not really, but what might maybe help is dev console in the newer versions. There is a command that attempts to fix the duplicate player/no player bug. If some of your saves can be loaded, you could try running that.