It is gorgeous.
I have a bit of yardage of light green gingham, small gingham either 1/8" or 1/4", 36" wide, so is truly "vintage", but probably not as old as your 50's & 60's, altho it could be... PM me if you want it. It is yours. It belongs with something as special as your quilt. It is in the same family of green as the green next to the coral on the far left, both on the edge of the quilt. It is not quite as vibrant as that, but I would classify it in the apple green category.
Facing it is a great idea.
If you want to bind it, I googled DWR, and found a possible answer to your question about that pointy square sticking out on the edges. None of the ones showing their edges have that square. You might consider taking off that square, that makes it all scallop edges.
https://www.google.com/search?q=doub...w=1280&bih=891