TipTip35,
The 767ER is nothing but international - Heavy Europe, all Africa and most South America flying. There are rumors that the ER will take over the Hawiian flying from the 767-400 which is considered a different category. They are getting the first of 13 (I believe) 757ER's later this summer that will be used on short haul transatlantic flights (JFK/BOS - West Coast european cities). The 767 domestic includes all 757/767 domestic and carribean and central american flying. There are unbid openings in the latest bid totalling nearly 100 FO positions on the 757/767 domestic and ER categories.
As far as gouge goes on the situational questions, just be yourself. If you excercise good critical decision making and command leadership skills you'll have no problem. There are not necessarily right or wrong answers. They just want to see how you process the scenario. For those wanting canned gouge answers - beware. The interviewers know the gouge info on the internet as well as prep services and will spot that a mile away. It can usually kill the interview because then they question if you can actually handle various scenarios that will inevitably come up on the line.
Good luck.