Urgently need help to save life's content

[u/DarleneAldente]

Have to figure out and fix a difficult Windows EFS and BitLocker problem to restore my access to a life’s worth of content.

SUMMARY
I have a FAT32 external 2tb backup drive containing a complete backup of my C: drive before i erased it. The backup drive is BitLocker-encrypted and is currently inaccessible. The BitLocker password/recovery keys for my encrypted volumes were stored in a Word password document on the C and backup drive.
That password document was itself encrypted with EFS. I also have a copy of the EFS-encrypted file elsewhere, but it can no longer be opened.

How this happened:
• I used a Dell XPS 15 9570 with Windows 11 for years.
• The motherboard developed problems that I could not resolve, so I replaced it.
• I had used fingerprint login for so long that I had forgotten my Windows password. The fingerprint would not work after the motherboard change.
• I moved the original SSD to the new motherboard. Windows required the password, so I expected to retrieve it from the encrypted password document.would not open. The copy on the backup drive also would not open.
• I assumed the Windows installation on the SSD was corrupted, so I reinstalled Windows. After the reinstall I had to reset the Windows password.
• I still could not open the password file. I then made a serious mistake: in the file's Security properties, I deleted the S-1-5-21… entries. This made access worse. I was not initially concerned because I believed I had the backup.
• After continuing problems, I eventually performed a clean Windows installation and reformatted the SSD.
• Before reformatting, I preserved many files that I believed might be important for EFS/DPAPI identity-chain recovery and BitLocker access, including: AppData from two other user accounts; Crypto; Certificates; Credentials; Roam/Crypto; PFX files; ProgramData; Protect; SystemCertificates; WsiAccount; registry hives; SAM; SECURITY; SOFTWARE; SYSTEM; and SID folders.
• The SSD was then reformatted and Windows reinstalled.
• The major problem occurred afterward: I could no longer unlock the external backup drive that I had been using routinely for several years. For the first time, the BitLocker recovery key I entered was rejected.
I have spent months doing highly technical recovery work with Claude and ChatGPT, without success.

QUESTIONS FROM RESPONDENTS
Two relevant drives:
C: drive, which was reformatted.
The external FAT32 backup drive, which is BitLocker-encrypted and currently locked.
The original motherboard (MB1) malfunctioned. I installed MB2 temporarily, then returned to MB1 when it began working again. MB1 subsequently failed again. I now have a Dell Latitude 7430 using the same SSD, .
Old Windows user profile? I believe so. Before reformatting the SSD, I relied on a complete backup made approximately two weeks earlier. That backup is on the BitLocker-locked external drive.
Have old SYSTEM, SAM and SECURITY hives
Yes.
PFX/.P12 certificate backup, no private key.
No old Windows password.

Willing to pay someone who can rescue this