just jumping in without reading all the pages (only pg 1)
the long stitches sounds like your stitch regulator is not making contact, push all the contections sometimes they get a little loose but feel like it.
It took me awhile to get my tension just right, my top is on the tight side when I pull the machine aside but my back and top stitches look awesome. The last time I had a thread break I changed the needle and no more breakage.
back to read more pages.