Welcome to the QB from SE Michigan! If your manual says not to use for quilting then I would not attempt to make a quilt on it. You do not want to ruin your quilt, especially since you are struggling already with the machine. There is a lot of weight to a quilt and management with a Domestic Machine is important. It is always good to learn to hand quilt. Be sure to secure you sandwich well. I prefere safety pins about 4" apart. This is a lot of work but worth it in the end. Then a hoop that fits your lap comfortably.
If none of this is what you want there is always long arm quilting to be considered.