Nice work!
One of the reasons your thread was breaking could be the size of the needle you were using? I just read an article from the website host, and the suggested size of the needle would be 90/14 ... and consider actual machine quilting needles. The eye is apparently bigger to cut down on shredding and breaking of the thread.
One of the hardest things about free motion quilting is keeping a consistent speed so that the stitches are close to the same size. It looks to me like you got that down really good!
THanks for sharing, and keep up the good work <g>