BreaMarrie has answered all your questions, she is once again wonderfull.(you had done it for me also the first panicking days, thank you sooooo much!).
I am mother to a two year old pku little girl, my first child, the only so far. Her name is Faye, she is healthy, smart, and terrible as only toddlers can be… I know how you feel, I can remember how overwhelming it is all this at the beginning.
The only thing I can advise you right now, is to take a deep breath, and enjoy your little one. It took me two months to realize that my girl has a metabolic condition of course, however she is also my precious one that grows up( and she grows up fine), and I shouldn't miss a thing….
Everyone here will reassure you that your boy will be healthy and normal. What it takes is more effort from you and for sure lots of worrying. But it becomes easier.
I am still afraid of the times that will come, regarding how I will manage with the diet as she grows older, if she will stick to it as a child. But as you baby will grow and be smart and normal, you will realize that she is like another baby. And more…sometimes I think that the patience she has when I give her all the vitamins, the discipline and program with her food are things that she will gain from in her life.
You will be fine, and you will meet lots of people ready to help you at this site.