not a true hour estimate, I like to get 4 guitars out of here every 12 weeks.
2 a surprising amount, things like going to the hardware store for sandpaper, superglue, PVA glue, stanley knife blades etc etc etc. Doing Manuals, I also take photos of the build as it progresses for the clients to remain in touch with their new babies. so I would estimate an average of one - 1.5 hours a day doing all that stuff.
3. Yes to some degree a 21/22 fret guitar does allow the neck pickup to sit in an "ideal" spot under the harmonic, however we dont seem to think that this should also apply to the bridge pickup??
I personally play a 24 fret guitar, and have a 22 fret guitar, and I dont notice any great differences, although my ears have been hammered over the years !!!
4. Not a lot, I spread the difference between the neck/body position and the bridge it doesnt account for a great deal. the distance from the nut to bridge is still constant.
a lot of this stuff I actually do automatically, the numbers are there in my head for when I need them.