I'm so, so sorry, Jane. What a heartbreaking discovery that your labor of love had been (temporarily) ruined by something you thought safe. I can only imagine the gasp, the panic, the "words" said (or thought) that would make nuns shudder, and some tears. All of the above?
I've read quite the gamut of possible solutions here, and had to chuckle at your hubby's comment about these cleaning products costing more than the quilt! I'm so glad you've found something that is working--with plenty of elbow grease, but still--it's progress and a HUGE relief to see positive results.
I've been using chalk pencils (can't remember the brand). One's grey, one's white. Is there any reason to be afraid that they're unsafe? My thinking is "it's just chalk" but then again, when some people have had trouble with blue pounce chalk not coming out, it makes me suspicious of everything.
The best testimonials --for the Crayola Ultra Clean markers--have convinced me of what to stock up on.
One thing's for sure: after bonding so much with this quilt, it will be your favorite for life!