sad to hear of the damage to your fabrics. Moths: use cedar balls and/or bay leaves to help keep them away. Mildew: use the dessicant you can find at WM ( in hardware section for drying out basements etc).
that said, i'm fortunate to have a daughter that sews for her family so the extra dressmaking fabric can always find a home. Periodically, i tell her to shop the fabric stash. I have too much fabric. My DH peeked in the sewing room when we were discussing moving a bookcase out of the living room, and suggested i downsize. i pointed out that would be like me suggesting he downsize his tools to make more room. However he does have a point. Humane societies often will take the mildewed fabric after it has been washed in bleach to use for bedding for the animals so even ruined fabric can be donated.