I've read most of the posts, but haven't found one that stresses how important the trimming is. After the block is sewn and crisply pressed, the ruler is laid on it so that the diagonal line on the ruler is directly over the diagonal sewn line of the block. Then you need to check to see that there is room on all four sides for the size you need. Then trim the top and one side. Turn the block around so that the other point is up. Now there are three lines that need to be lined up exactly. The diagonals should line up, but the bottom and one side should line up exactly. Then you can trim the other two sides. If you have a turning mat, that would help and so would a ruler that is the exact size you want your block to be.
I got rid of "swinging" by using my stiletto (purple thang, chopstick, end of a seam ripper, little stick sharpened in the pencil sharpener, or what have you) to hold on to the very end as it goes into the needle. My treadle is really good at swinging those ends.
Using the glue is an excellent idea. And then sew through the cross hairs of the preceding line of stitching.