And "cutting" off the binding might be the easiest method to remove the old binding.

Nothing wrong with the quilted front--------------just cover the back. Not sure it's even necessary to HIDE the old black. Bro knows what happened. He won't mind the black showing thru the new RED back.

Use your rotary cutter to cut the binding off. You won't lose much in either width or length. Fuse a patch on the torn spot to stabilize it and then put a new back on the quilt and quilt it lightly to hold the backing to the rest of the quilt and to hold the fused patch in place. That will save the quilt and will add to the quilting design on the front. You will think it is a planned design element.
I'm sorry this happened to you, but you can make a lemonade out of this lemon. froggyintexas

Did you prewash this fabric before you used it? I'm just curious. What a cool quilt your created, I'm sure putting on a new backing and binding will make it perfect. If I lived nearby I would take your binding off for you. Perhaps you have a quilting friend who would help?

Years ago there was an entire line of black fabrics which disintegrated right away. It was a nightmare for shop owners and quilters as well. It was determined that a particular dye was the cause. So sorry this happened to you.

So all of the best ideas or ones I would have thought of, have already been given to you, so all I can do is send you Hugs & Kisses!!!

I agree with a lot of quilters on this site that said leave the old backing and put on a new one and then I would turn
it under all along the edge and butt it up against the hand sewn binding on the back and machine stitch it down.
Unless you feel it's not a big deal to unstitch the hand sewn binding on the back and then re-stitch it to the new
backing. That would be my first choice. Then I would machine tack it.

Looks like a cat or dog got a hold on it to me....is that possible? My dogs love to scratch anything they decide to lay on.

I have a thought on the suggestion of leaving the binding on and butting up the new backing to it. Wouldn't the original binding be at risk of coming loose if it's attached to the old backing which is shredding?

I'd put a new backing over the old. I'd take out the handstitching on the binding, open up the binding and sew over the original machine stitching that attached the binding in the first place, this time catching the new backing. Then hand sew the binding to the new backing and tack stitch with my machine to hold the backing in place.

This has been suggested previously, but I thought I'd add the part about the original binding coming loose. Whatever you do, good luck.

I had trouble with direct sun coming in on the same side of a hand-quilted quilt; I was young and did not realize what I was doing. I loved this beautiful quilt from my mother-in-law. The fabric became so fragile it would rip if we even turned in the bed.

I don't have a better solution.