How To Repair Corrupted Partition

My 3Tb HDD recently started acting up. I use SSDs in a RAID0 to boot with and pretty much everything else, including desktop, downloads, documents, etc. are redirected to the HDD. It started with missing icons for shortcuts and then folders became inaccessible with an error message of "The file directory is corrupted or unreadable." The folders, that contained plenty of files, were reporting 0 content and more folders started to become affected.I restarted my computer hoping it was a temporary glitch but now windows is telling me the drive needs to be formatted. Disk Management reports the drive to be operational with 2794.52 GB RAW and Healthy (Primary Partition). I booted linux from a USB stick and was unable to mount the drive. Kaspersky Rescue Disk simply doesn't recognize the drive. Possibly the oddest thing, though, is that EaseUS Data Recovery software is reporting only about 770GBs for the partition. Whats strange about it is that's right around the amount of free space that was on the drive.

I haven't run a CHKDSK or checked for bad sectors yet because I'm hoping to try to recover the files if possible. I have backups of the important files but there's a huge amount of data that isn't backed up that I'd at least like to try to get to before reformatting or doing something else that will ruin any chance of recovery