FAC is a B billet, but since it's only a year, you'll usually back is up with something else before coming back to the fleet, unless you got crap-canned to it between deployments at a sqdn. If you complete a full sqdn tour, then FAC, you probably want to either hit a school, e.g. EWS, or another non-fleet billet before going back to a flt sqdn. Most savvy captains would ask for flt school. Of course, why do FAC, if you can get IP right out of the sqdn, anyway? Like everything else, do well, and opportunities tend to present themselves.
As for your ?
Overseas is not hard to get--the monitors usually have a hard time filling those
You can definitely come back and fly primary for SNAs or SNFOs as a helo bubba, FAC or not. You only have limited choice as to whether you go VT or HT, however.