Are two 30 minute sessions of cardio (morning/afternoon) enough?

its more than enough. too much cardio is horrible for your joints. I used to do 2 hours of cardio at a time on a daily basis and my knees are still a bit hurt. If you wanna get muscular lift weights. Your not overweight your fine. Your doing cardio 7 days a week and for a total of one hour. Increase your weight training and limit your cardio then you will buff as hell.