I put my stitch length at 12/14 per inch wich translates to 1.5 on my Bernina. Your stitch is to small if it is bunching up.
There is no need to either back stitch or drop your length to 0. As long as you sew past the intersection or into the seam allowance several stitches. I have never had any seams come apart. If a few stitches get loose at the begining or end of your sewing it is okay because those stitches are not actualy part of the sewn seam. They are before and after the actual seam area.
I only pin pieces if they are large and flop over. I keep a lamp next to my machine and hold the paper section up to the light so I can see through the paper and line my fabric up with a 1/4" allowance over the line on the pattern piece.
You will get lots of help here from people and also do a search for some tutorials.
peace