Bob almost certainly knows how to create a dark hallow.  He was, after all, there when the dark hallow ritual was formed.  And by there I mean there on Harry's side (while occupying a dinosaur).   

Harry had him forget the Kemler bits, but that would not apply to the bits he learned while serving Harry.   Also keep in mind that the dark hallow principle was incredibly obvious to the wardens when Harry explained what was going on. It is pretty obvious that Bob could have been equally quick to understand the basic mechanics based off a very quick observation.

The point isn't that Bob knows how after Dead Beat or that Bob could figure it out during Dead Beat. The point is that Bob knew how Kemmler had described the Darkhallow after Harry had ordered Bob to permanently forget his time with Kemmler, limiting Bob to only general knowledge of Kemmler.

"On the queen's level" is interesting.  So it could have been a Walker?

Yes, it may have been. Harry describes the walker in Chapter 43 as not bigger, but deeper than Mab and having power "beyond anything [he] had seen, beyond measure, beyond comprehension-just plain beyond."

On the other hand, the power of the Walker could be sufficiently different that it couldn't have manipulated time at all.

Maeve does something similar after Harry rescues Molly from Arctis Tor.

I think this is what Kringle was referring to and is why I said that it was implied that a Faerie Queen that did it.

I think there was an implication that a Faerie Queen was doing it.

That's a stretch, but it's workable. Bit of a retcon.

@ peregrine: I was trying to find something that was more specific than just feed to forestall the argument that feeding doesn't necessarily mean biting.

@ Snark Knight: There is a reason I was equivocal with all the may have's.

The reason I've always thought that it was more than just a spell is that the fire behaves weirdly, and it stops Harry's heart. Then Michael beseeches the Lord on Harry's behalf. Michael says "[Harry] deserves better than to die here, Lord!" Then a little later Harry as narrator says "[a]nd then my heart lurched and began to beat again," which could just be a case of CPR standing for "Clean, Pretty, Reliable."

There is a lot of rules inconsistency in the earlier books. This whole scene may be operating under slightly different rules than later in the series, and that explains the oddness of it. Or there is something more going on.

Furthermore, an otherwise healthy wizard might be able to throw a death curse and have a doctor on standby to get them going again. We don't know and neither do wizards. Luccio thought her wound was fatal, but a doctor who doesn't actually practice medicine, let alone trauma surgery in the field, was able to keep her from dying.

I am thinking that Margaret let Eb in on her plans to create a star child with Malcolm.

Here is some WoJ:

At what time did Ebenezer know that Harry existed, and does he know that Thomas is his grandson.
Not until it was too late.  Not till after Justin’s death that he was able to find out.  As far as Thomas, Stay Tuned.

This doesn't mean that Eb didn't know Maggie was planning on having children with Malcolm, but it does mean that he didn't know that Maggie was pregnant. When Maggie died, Eb didn't know to go looking for Harry to keep an eye on him.

It is children, siblings or parents of anyone targeted.   If my parents are dead, it does not sound like it would jump automatically to grandparents. 

It did jump Bianca, Ortega, and Ariana to get the Red King.

The problem with Bonea is that she has no understanding of the knowledge she has. She probably won't realize what's important, related, or relevant most of the time.

Like most children, getting her to help out on various things will be more about teaching her than getting any actual help from her.