Just to confirm then, your most recent backup would still give you game saves from at least 12 days ago?
Ugh. No, there is nothing you can do as a regular Windows user with the tools that Windows gives us to recover these files and I would not recommend trying to extract data out of .bad saves. We don't know what exactly went wrong and where when a save is not successful, even if the file sizes of the component world nhds look right. Also the component world nhd files might not be as useful as you think if the TravelDB that holds everything together is not also intact.
In theory you could take this computer or at least its hard drive to a tech specialist and have it examined for potential data recovery -- this will cost quite a bit. as in potentially hundreds of dollars (USD) and may not end up recovering anything useful. The data might still be there but Windows has no way to find or point to it, the more you use your computer since this happened the more likely the data will become overwritten as hard drive space is used for other things. There are also data recovery software programs out there that again in theory might be able to help, but the effective ones are not free and in the end you may still end up with nothing usable.
Although it may seem catastrophic right now, we're only talking about 12 days of gameplay loss and not files that are critical to one's health, education, career, or financial well-being. I'm afraid that if this happened to me and I had no viable backup source, I would take the loss and as best I can replay the lost days with the understanding that not everything is going to go or get designed exactly the way it was the first time.
