Your quilt is just lovely! I made seven flannel quilts for the family back in 2005 and just finished another batch for the family. Flannel is not woven as tightly as cotton, and it can be somewhat stretchy. I found batting such as
warm and natural or 80/20 batting is better than wool or polyester because the quilt top can get mushy during the quilting process, and it is easy to get puckers this way. On my longarm, I found size 18 needle works well for FMQ. Also it helps to zigzag or serge around the edges before binding. Keep the quilting simple. Quilt books with patterns for flannel generally give basic guidelines on working with flannel.