I think this is totally normal behavior for a newborn. They nurse to eat, they nurse for comfort, they nurse to help your milk come in and to regulate it. They also have to tell your body when to make more (i.e., during a growth spurt). I think it's pure coincidence that it started at the same time as the PKU.
I'd stay stop the binky and the gripe water (unless he needs it) and give in. This will pass. Let go and let your pre-schooler watch his favorite shows. That's not normally a suggestion I would give, but for now (with the newness of your newborn) it will help and soon enough you'll get back to normal (ish).
I'd also suggest wearing baby in a sling or wrap in which you can nurse. It helps if you're not always having to hold him and can do other things (though don't cook while holding baby in one, and be very careful when you bend over).
Co sleeping at night will also afford you more sleep. It really helps to be able to nurse baby when he needs it but still sleep a little yourself.
It's important, especially in these early weeks, to nurse on demand, rather than just when you think he should eat. Babies don't just nurse to get more milk. It's also to help your supply to be enough for him. You may not have experienced this with your first, but all babies are different. But for a good nursing relationship (and so you won't have to depend on formula later to supplement) you need to nurse on demand right now. Many women end up supplementing because their milk doesn't come in or they don't have enough, but honestly, if you nurse on demand, it is baby's (and nature's) way of making sure your milk comes in like it should. Nothing is more pure, whole, and organic than mama's milk!!! And it can't be contaminated.
I've been there. I'm a SAHM of a 3.5 year old, a 20 month old, and a 2 month old. It does pass.
Good luck! Invest in a good sling or wrap. I have the Moby wrap and the Maya wrap sling, and they are both great. Or look up how to make them. It's pretty easy!