wesing, I feel for you, same thing happened to me. I have a different machine.
I know when I tried mine the first time I wanted to throw it away too.
I put two white flat sheets and batting together like I was making a quilt (so not to ruin a quilt). I did all the same things you probably did. Called everyone that I thought new anything about sewing. Nothing helped.
Finally after a few days, it just out of the blue, started sewing right.
No more thread breaks.
I believe we just need to learn to get our arm movement syncronized with the speed and stitch length. I don't know if this makes sense.
What I did was, begin with a slower speed on my machine and the movement of my arm and slowly increased the speed and movement of my arm to keep the stitches even in length
Practice, practice, practice.
I practiced different stitches until I quilted the whole piece, then used it for a mattress pad.
Good luck.