I don't like the Connecting Threads thread, I find it produces too much lint. I have tried many others but always end up going back to the Mettler brand. The poor bobbin stitching I am sorry to say is probably inherent with the sewing machine. You might try switching to another high quality thread like Mettler, Presencia, Gutermann, or Aurifil to see if that helps but I kinda doubt it will. The Presencia and Aurifil really do produce less lint but are too expensive for me to justify their usage. I think you need a better quality sewing machine! I sew on a Bernina purchased 19 years ago and still love it!