Your not alone, everything in your post sounded exactly like me, only difference am only allowed 4 exchanges!!! It is very hard to control this diet, its like a weight loss diet you get bored and then you cheat. I get bored on my PKU diet and cheat and 1 does lead to another and another and then you soon realize your back to square one.
My motivating factor is also about high levels and how it affects my loved ones specially with my 2 little girls. I am doing this diet not only for myself but for them. I cant be that moody, short tempered, no energy or time for them when am off diet.
I think its great your studying to become a dietician, and determined not to let PKU get in the way, like PKU got in my way and stopped me from doing things i wanted to achieve in life!