Try lengthening your stitch length a little. That should help with the puckering.
I'm not sure what it is about the bobbin thread that you think the tension there is too tight. It's much easier to adjust the upper tension. If top thread is being pulled to the bottom, increase the upper tension number to make it a bit tighter and it should pull the bobbin thread more into the middle of the fabric layers. If bobbin thread is showing on the top, decrease the top thension so that it won't pull as tightly and will relax the thread into the fabric layers. Do not be afraid to change thread tension. Sometimes it's what makes the stitches look like they should. And- like someone else mentioned- there are many things that can cause stitches to not be "right". I won't list them all again.
Tracy in Nashville, TN
Martha Pullen Licensed Educator