Several things will help. Did you know that Ricky Tims quilted all his big prize winning quilts on a Bernina with a 7 inch harp. He free motion quilts. That being said I also have quilted a small king size quilt on my Bernina 7 inch harp machine. I stitched on the diagonal one half of the quilt at a time from the center out! So yes it can be done.
First to stop the drag on the quilt I find it must lay flat going into the machine. Either get a large flat extension or a table that will drop the machine down to have a flat surface.
Second I find pinning difficult due to my fingers with arthritis. So now I spray baste everything even my hand quilting. I have used most of the products but really like 505 spray.
Third Relax and try to quilt small sections at a time. work in quarters. Yes from the middle out!
Watch tutorials and perhaps make a matching table runner and practice on that.
Let me know if you need more help. Good Luck and have Fun!