I believe the black fabric plus wool batting is your problem. I am hand quilting a quilt that has thin strips of black throughout, and it's a real pain in the neck, because the wool batting coming through the black fabric is getting entwined in my quilting thread, and stopping to pull it out is really slowing me down.
I don't know why wool tends to beard through dark fabric, but this is not the first time I've heard of it. I will never again use wool batting in a quilt with black or very dark fabric (I used Quilter's Dream wool, so apparently the brand isn't the issue).
I plan to finish my quilt, which is small, and then suggest that it be used as a wall hanging.