Answer to #2. If you use charm squares, the yellow would be 5" cut and 4 1/2" finished. Then the 1/2 square triangles that make up the pinwheel square would finish at 2 1/4" each. You would need to cut the charm square down to 3 1/4 each or just sew the diagonal 1/4 each on each side and trim finished blocks to 2 3/4". You will have a lot of waste if you just use charm squares. If you use the charm squares whole for the pinwheels, measure you finished block and cut the yellow the same size.