I totally agree that machine quilting with a shortarm machine on the dining room table is a hassle. One of the main reasons that things go wrong, is the weight of the quilt vs the height of the machine. Gravity fights you every step of the way.
My first suggestion would be to check second hand stores for a sewing machine table that has a well in which to place your machine. This will put the bed of the machine even with the work surface.
Secondly, when working with a large quilt consider changing the way you face the machine. I roll large quilts and quilt facing the head of the machine. In order to do this comfortably, I place the sewing machine table against the dining room table and put a card table on other side with machine sandwiched between. Then I put my chair at the head of the machine. Starting in the middle of the quilt, I can then slide the quilt back and forth with no pull from it's weight.
I hope this is helpful. Let me know if I can be of any more assistance.