Personally, I'd throw it ALL away, along with the bin. Here's why.
Mold spores cannot all be seen so you really can't judge what LOOKS mold free to actually BE mold free.
There is no way to know how long it's been sitting in that condition or whether the bagged fabrics were bagged up only for the yard sale because they looked cleaner than the others.
It clearly came from a source that had very low standards of care.
There is a risk of spreading spores to other areas of your stash, house, etc.
Someone who is extremely mold sensitive may wind up with a quilt made from these fabrics.
The risk, work, and worry are not worth it to me. I'm just not that desperate for fabric.