My name is Breanna. I am eighteen, and I have PKU. First of all congratulations on your new baby boy! Try to enjoy him the best that you can, because although I know times might be trying right now he'll only be little once. If you ever have any questions please feel free to ask, and I will try to help when I can.
I am sorry that I cannot be much help with this topic, but my mom has breastfed my two younger sisters who also PKU along with our six siblings who do not have PKU. She also teaches child birth education classes as a living, so this is by far not a foreign subject for her. If you want to send me a message I can give you her email address if you would like to talk to her. I am sure she could offer you plenty of ideas both PKU and not PKU related.
Take care, and as always let me know if there is anything I can do to help.