First check your tension on your machine with leftover scrapes from your quilt and batting. That may take care of the thread problem. Another thing to remember is when you start, put your needle down and then pull out the thread from the bottom so that you don't have that bobbin thread gumming up the works on the back. I usually go to an area that either I'm not going to quilt or going to do later so that the threads can be pushed out of my way until I can get to a space to safely clip them without having to move my quilt and take the chance of messing up my pattern.
Another suggestion may be the speed that you have your foot pedal working. This is going to sound goofy, but I put on hard rock when I quilt. I find that I push my foot pedal down faster and move my hands faster keeping up with the beat I know, I know -- just me! It's a mind thing :oops: ) It seems that the faster you move the needle and the quilt, the smaller and more even the stitches.
I've been machine quilting for about 7 years now. I'll be honest with you and tell you that it took me probably 6 months before I liked the way the quilting looked but then again, I was only quilting on the weekends because of work. It takes time and practice. :-( .
Don't get discouraged. Even God took 7 days!
Hope this helps.
Lee