The recommended intake for "normal" people would be 50% of your daily calories come from carbs, 30% from protein and 30% from fats and sugars. The main issue for bypass patients is that we don't (At first anyway) absorb all the nutrients that we consume so we have to increase our protein intake to prevent our bodies robbing our muscles and internal organs of protein for fuel.
I would suggest Jo that you concentrate on getting at least 70g of protein in per day. Make sure your getting at least 1000 to 1200 calories a day with as little fat and sugar as possible, and the rest will take care of itself.
Every NUT and surgeon you speak to will have slightly differing views on it but most of them are fairly consistent on the protein first front