While I'm no expert, the way I understand the idea behind Pop's Brine formulation is that compared to many other brine recipes you might see, Pop's is less salty. To that end, you use a longer curing time. This allows for more margin of error in that you don't have to get it pulled out right away for fear of over-curing. With a saltier brine, you'd better pull it out at just the right time otherwise you've over-done it.
With Pop's formula - you won't shoot yourself in the foot if you go a few days longer than you planned (if life gets in the way or something).
I'll be butchering half a hog later in the week and plan to use Pop's brine for some bacon and then for a whole ham. I plan to use his "full strength" version and then pull it at the shorter end of the spectrum and fry up a test piece. If its too weak, back into the brine it'll go for a few more days.
As far as how to know when its completely cured goes - provided that you've followed the guidelines - from what I've read, the bellies should have a fairly uniform firmness to them. If they are still mushy or soft, they're not done. But you should wait at least until the 10 day mark (esp on the half-strength one).