Brother 1500s

Question

i do not have a problem sewing regular stitches. when i try to do the free motion quilting my thread keeps shreading and breaking.. sometimes it will sew for 12 to 15 inches before it breaks.. i have changed the needle and the tension and the bobbin tension but still no luck.. so frustrated with the machine now.... it seems that the upper tension is too tight but i loosen it and cant get a good stitch... when the feed dogs are down the machine will not sew. please help. i have worked with it for 2 days unsuccessfully. could you tell me what needle i need to use what thread and where should my tension be set on the top and how tight on the bottom... the book says the bobbin should be the same as the top but if i do that the thread is too tight.. It is probly me but i can get the machine to sew wonderfully if i want to sew straight sewing..this is 1500 s brother..... iva