I just wanted to add, for anyone reading the thread from top to bottom.
Our son is Hyper Phe/Mild Pku. I believe that makes a difference.
I was reading some posts last night, old stuff, just to help educate myself. My calculations are certainly easier and less to take into consideration, then those who are CPKU. I don't have to measure any Phe levels. I simply count proteins that he consumes, and ensure they stay in the low range set out for him. I have some measuring, but it seems to be more about volume control then phe levels. Much easier for us.
(I just didn't want someone who was CPKU, to use my way of counting, as it certainly would not be accurate for someone who measures Phe, maybe it would give an estimate, but that wouldn't be good enough)