Just a thought also, when Alfred first spoke to Harry, it caused him pain. Bonea was causing Harry's headaches. Maybe that was her trying to talk to Harry but lacking the proper frequency.

Mab knew this but says nothing because she wanted a lever to manipulate Harry. Alfred just doesn't think about these things unless Harry asks. Harry asked how to get Bonea out, not how to communicate. It took a meeting with Id-Harry to introduce her as something other than "the Parasite". Until then Harry didn't know Bonea was potentially a friendly.

Most likely, she didn't know how. She was still developing. Her ability to help keep Harry alive was probably only possible with step-by-step instructions from Mab and Alfred.

The Island. Not the beings. We heard that Edinburgh is also a nexus. Chichen Itza. I think they look at the lines like settlers may have once seen a waterfall. Hey, there's a place I can build a mill! Water power will grind my grain! Steel towns popped up around coal. We know the stones of the buildings have power infused - Merlin likely tapped the Well. Maybe they STILL tap the Well for power. Maybe Merlin harnessed that power to create Alfred... maybe it powers Alfred, and that is why he needs to stay near/on the island.

The Lines draw the building of the Wizard HQ, or Demonreach. Or Itza. The prisoners don't generate them.

We also hear from Bob in Cold Days that the waste heat of the prisoners is what powers the ley lines. No prisoners, no energy. The ley lines are also coming from the middle of a body of water which would normally disperse the magic. Merlin probably set them up to bleed off excess power or the pent-up power would have exploded by now.

We saw how difficult it was to get Ethniu into the Well.  We saw how difficult it was for Harry to fight Shagnasty… how did the inmates on Demonreach get there?  Who put them there?  When did they get there?

I suspect we'll never know unless Jim decides to do "History of the Wardens and White Council" series. Demonreach is an interesting story element but one that raises more questions than answers.

If someone powerful enough to use the EYE is after me, the last thing I'd want to do is trap myself in a circle. I can see having them on a prepared escape or ambush route though I doubt you'd have the time or the power to make one capable of withstanding a blast.

Harry made Little Chicago by gathering all the components from all over the city on his own. Marcone has hundreds of people to take pictures and gather materials and has the head start of Harry's work to build off. Yes, there was a great deal of destruction but 60-70% of the city is still there and Marcone would be able to get a full picture of the damaged areas much sooner.

We know that Harry's basement survived total destruction in the fire but did Little Chicago survive? If it did the FBI could have moved it or Marcone could have taken it. Namshiel would be able to fix it and Marcone couldn't fail to see how useful a tool it was. He'd get more use from it than Harry. He may have moved it during the castle's construction and not moved it back.