Direction - im trying ti figure this out too. One guy i talked to does both sorta - he’ll pass the awl from in to out until just the tip shows, then chase that out to in, but I think his argument was more about the shaft and curve of the awl over-stretching and weakening the holes.
Popping - I had to fix a couple of pops, frommer showed a method of creating a short tunnel through the more central part of the insole and running the thread through it then going back through the broken holdfast to return to the usual spacing in the upper. My only personal thought on that was make sure to do it twice in a row, that way the loop that makes that trip is pulling on a u-shaped chunk of insole rather than the thin roof of a single tunnel.
Length - ive seen a lot of variation too, since you’re doing 3/4 welt western style the only advice from the frommer book is make the channel the length of the forepart featherline to where it disappears on the medial side and reaches the shank on the lateral. That transition looks to be roughly where a line perpendicular to the axis of the shank would meet the end of the feather line on the medial side. Picture from Frommer book
