The time to clone your hard drive is BEFORE it gets screwed up.
AFTER it is screwed up there is little point.
What I'd do in your situation is install a virgin drive in the computer
reinstall the OS on that drive then "data mine" your data off the failing drive.
As soon as you have all your data and settings working correctly on the new drive clone it again, to another new or new-ish hard drive.
Frankly if an OS screws up on me I never again trust the drive it was on
regardless of what testing shows it as good.
I've taken drives that others tested as "good", copied them full of mp4 files
with CRC information included, and found errors, repeatable errors, when copying files back off of the drive, errors that were not on the parent source....
Frankly I consider my time to be worth a minimum of $75/hr
if a failed hard drive costs me an hour due to it's failure it's cheaper to replace the drive so I don't need to restore everything twice
Time is money, drives are cheaper than time