As I read this post it occurred to me there *might* be a way to stabilize this top before you wash/clean it.
You could add a backing of muslin to the top -- NO batting -- using the birthing method and using a larger stitch which you could remove/pick out more easily after the washing.
After the 'quilt' is "birthed" (turned inside out), you could 'tack' or baste the two layers together every few inches using a thread and stitch that you can remove later after washing and drying the 'quilt'.
Wash on very gentle/hand wash settings, or in the bathtub if you want to deal with the bulk of the thing when it's wet.
I personally probably would not dry it in the dryer - to avoid any more tumbling and risk of the original stitches and seams coming apart. If the weather is decent I'd dry it in the yard, in the shade, between two sheets for an hour or so. You could do a little pressing while it's barely damp before removing the basting stitches and the backing attachment.
Jan in VA