I lost the post I started...hope this is not a duplicate. Do not mess with your tension! If your tension is OK with a straight stitch, then the tension is OK for your FMQ. Nine times out of them the problems you are having is your needle SIZE..one reason your metallic needle is working better.,...it has a larger eye. Try a 90/14 microtex needle, if you don't have one, then use a 90/14 topstitch needle. Your needle has to match your thread, then you need to consider the type of fabric you are quilting. Check with the thread manufacturer to see what needle size the recommend for the type and weight of your thread. Ask me how I know....had your same problems in a FMQ class....
after 20 minutes of frustration, broken needle and broken threads, I too the cone of the spool and luckily inside the spool the manufacturer had the needle recommendation for that weight of thread. I changed needles and it was smooth sailing from then on.