In the past decade I've repaired 2 quiltd like this for other people.
I spent three nights taking all the stitches out and separating the back from the front (and discarded the lumpy batting on one).
Then I repaired the piecing on the front.
I layered the repaired top, new batting, and backing (one I had to completely replace),
and requilted and rebound them.
Good as new!
Jan in VA