wow, that quilt was loved to death or maybe wasn't sewn the best to begin with or fabrics weren't good quality (apologies to great-gramma). I'm amazed that you took this project on, and did such a great job salvaging it (like others said) ... if it comes back to you again, I would just put a new back on it, new top and let all the other stuff in the middle, LOL.
Thanks for sharing, I've never seen anything like this b4!