With (1), separate characters absolutely read the situation, every man for himself. The answers to the questions aren't going to be the same for each character, and only the person who did the read gets the +1 bonus. So everyone who's interested should make their own unique read.
For (2), it depends on what was going on. It sounds like you figured that the battlebabe could act under fire to lead the others through the camp? She's the only one who needed to roll, then.
It doesn't hurt for the others to help, though, and you would imagine that they'd be doing their best to help keep from getting caught ... probably it would have made sense for each of them to roll, if they're actually contributing in the fiction. If they're just kind of dawdling along after the battlebabe, though, then maybe not. To do it, do it ... roll to help whenever you're concretely helping.
Remember that, theoretically, helping rolls and hindering rolls are declared before the main roll's dice hit the table. You don't need to be strict about that, but that way it still makes sense for two people to help, even though only one hit will count. It shouldn't be, Dude A rolls to aid the battlebabe and gets a hit, so Dude B goes, "Ok, it doesn't do any good if I help, so I don't."