I am using #8 perle cotton to do a redwork lap quilt right now. I am using the back stitch method which will be using a bit more than a running stitch. I did 1 row of embroidered verse around the outside of about 45 X 60? I also am doing a leaf outline in every other block. It is less stitching than you have on your sketch and I am just about done and I've used about 1 ball and 1/2. Mine were 10g balls and maybe that will help you guesstimate your needs?