Thought I'd throw in my experience, being 12 days post op from a Nissen.
I have not had difficulty staying full. Since the surgery, my stomach has a different idea of "full" and its about a cup of food a meal, maybe a bit more lately. It was not difficult to stay nourished during the liquid phase by drinking ensure through the day, you actually get a decent amount of calories.
Now that I'm up to pureed foods, I don't feel nearly as restricted. I've had all kinds of soups, mashed potatoes, overcooked pasta, ice cream. I just eat slow and listen to my stomach to know when its full. Haven't felt hungry at all.
I used to get hungry a lot and I thought after the surgery I would be constantly starving. That was not the case.
Hope this helps. I also agree that your doctor may have some solutions for your concerns. Its just day 12, but the Nissen has already been very good to me, so I only have nice things to say about it.