In addition to what Bytepusher posted, if you wanted to leave the airport and come back, then 4 hours isn't really a huge amount of time especially since there isn't really anything around the airport area which would be worth going through that hassle for, and, probably not enough time to get to somewhere decent. If you are on a connecting flight and your bags are being re-checked in for you there is probably security issues as well.
No and no
(Ok there is a small museum just outside Terminal 1 domestic security where you can kill 15 minutes).
There are two terminals and each has an area outside security and complete separation between domestic, transborder and international departures so in all there are 8 separate areas where an individual restaurant might be located, you will have access to, at most 3 of these areas, more likely 2.
At present the dining options are universally poor and expensive, mostly chains like Casey's and Turtle Jacks and Fionn MacCools. A couple months ago Mill Street Brewpub opened a location in the terminal 1 domestic secure area so in that case you can at least get decent beer (provided you don't mind paying 9+ dollars a pint)
The airport has announced that they've signed a new deal with the same company that has redone the food at JFK to some acclaim and they've signed on a number of celeb chefs to put their names on them, nothing opened as of yet and it won't be fully in operation until the end of 2013 it remains to be seen if this will actually deliver on a quality improvement, it certainly won't help with the overpriced side of the equation.