Partition became Unallocated, files seem to be there somewhere, need to get partition back!

[Benjammer666]

I was messing around with software that changes your boot drive called EASY BCD and I think it somehow messed up one of my drives partitions ( I wasn't even working with that drive, but that's the one it chose to mess with it seems).
Also could have been due to plugging and removing my backup drive using an external USB and hot swapping a few times.

I'm 99% sure my drive was WAS just one big NTFS partition, now it's somehow split into an 2TB and an about 9TB unallocated partitions. It's a 12TB Drive.
I remember it was about 11tb actual usable capacity. And Microsoft Disk management says it's 11,176gb, However, in TestDisk it's reading it as 12TB / 10 TiB which is a bit concerning along with the message that it needs to KNOW THE RIGHT SIZE of the drive.

Initially after quick analyzing it finds 2 small / identical MS reserved partitions as well as the main one with my old drive name attached and it says MS Data.
If I try to list the files there it says Can't open filesystem, seems damaged, which is concerning...

BUT if I get out and go to Advanced Filesystem Utils, I see one Microsoft reserved partition, and my old Data Partition and there I AM able to successfully view and restore my files!

It says the boot sector is OK I tried rebuilding or using from backup and it says it's identical (nothing to repair?). One thing that stands out about the bootsector thing which seems odd is that Clusters per mft record is -10 (but maybe that's normal or because it's unpartitioned right now basically).

I don't have another drive large enough to back up everything, I'm hoping I can just tell it to fix / bring back the old NTFS partition since it knows the files are still there, just don't want to do anything wrong and make things worse.
There's an option to load a partition from backup in the main section, is that first MS Reserved thing the backup partition or something else? It's only about 16mb I believe.
I haven't tried doing the deeper search but I don't think it's necessary (correct?).

I also haven't tried attempting to use MIcrosofts built in disk checker tools in my experience it just makes things worse usually.

Thanks for reading, hope it makes sense, if not I'll try to clarify. Thanks for your help.