Looking at your photo, I see that you have your machine on a regular sewing machine table. This will never work out well for a large quilt, as it is certain to fall towards the floor both front and back as you work on it, with the weight of it making the quilt very difficult to maneuver and turn. I think you'd find it much, much easier if you can do your work on the largest table you can find that provides a comfortable height for your machine work. Maybe you could find a church or other meeting place that would let you push two tables together and put your machine on those to work on your quilt.
Not that it can ever be easy to actually quilt something this big on a home machine with a small throat space. And of course it's not realistic to suggest that you run out and spend the money for a longarm machine (to say nothing of finding a place for it).
I'd try to find a longarm quilter who would quilt this for you for a price you're comfortable with--you can check out the classified sections of various quilting magazines for people who do this work or you could ask for recommendations from local quilt shops or guilds.
Good luck with this quilt. It will be beautiful when you're done.
L.L.