ok, so - if you want to airport loop specifically, then i would recommend that you indeed either glue, melt, or tape your knot (i usually use electric tape if im airport looping) this will prevent the knot giving and the chuck flying across the room.
1) thickness of rope is totally a personal preference thing, i have used lots of different thicknesses, hehe
2) the number is the weight that the cord will hold before it actually gives out
3) tape it if you must airport loop - i prefer a bowtie, or double slipknot myself.
5) if you want to hide the knot on a pair of wood chucks, the horizontal side hole is the place you want to do it. There is a guide somewhere, and im sure someone else will post it, of exactly how to retie them like they come.
6) making equal loops for an airport loop is really a trial and error thing, and a matter of taping one knot and then making the other one the same.
7) I dont know how good it is, but i did make a video for tying chucks the way i liek to tie them, hehe.
Hopefully this answers some of your questions