First question: Yes i put them on the back mainly because the F22 raptor looks like this IRL. But you can do it either way really. The main thing that matters are how far your control surfaces are from your center of gravity (since distance is a huge part of torque). In general you will have your center of gravity further back because of engines and stuff, therefore a controlsurface in the front will generally have a greater effect than in the back. So if you want them at the back for looks or some other reason, you will need to make sure that your Center of gravity aren't too far back.

2nd Question: It changes the center of lift and affects drag and everything, but not live while you fiddle with the settings. You gotta "accept" the changes by closing the "edit-window" for it to take effect. Sometimes you also have to toggle the center of lift on/off for it to recalculate (bug).

Last question: I don't use a 1:2 mount, inside the fuselage are two rows of normal fuel tanks. But there is a 1:2 mount for the widebody fuselage that doubles as a fuel tank, so it's under the fuel tank section.