I spent time trying to figure out what is happening with your installation.
Obviously the bootloader was working since the boot test worked before your could start the encryption. Decrypting doesn't affect the bootloader until the drive is fully decrypted so pausing the decryption doesn't have any impact.
Since you didn't even get the VeraCrypt password prompt upon rebooting, it means your bootloader has been corrupted or your hard drive has read problems.
You message today shows that the bootloader is OK since you can boot from USB (This only adds to the mystery!). The bluescreen of Windows is due to the fact that Windows expects Windows to be on internal hard drive and not USB and that's what is causing the
I think the most probable reason is that your hard drive is starting to show signs of fatigue/defects and that's why the bootloader is not always read correctly.
In order to retrieve your data, the most reliable way is to use the rescue disk created by VeraCrypt when you encrypted Windows : put back your old hard drive on the PC as it was before (SATA/IDE, not USB) and boot from the rescue disk : in the password prompt,
press F8 (repair) and there you have several options.
- At first, you can try "Restore VeraCrypt Boot Loader" and see if you can boot Windows again.
- if this doesn't work, then you can choose "Permanently decrypt system partition/drive" : this will decrypt your hard drive but much slowly than under Windows.
I'm confident this solution based on the rescue disk will help you decrypt your hard drive. Of course, this supposes that the hard drive is not defective.