Where are the details on how to interact with the U.I. for Mass Effect?

The key for interaction is space bar by default, which may be confusing because in most PC games that would be E. (It used to be E in classic Mass Effect 1.)

I'm not sure how you're supposed to know this. It looks like a design oversight, because when you play with a controller, there's a button icon next to 'investigate' and 'talk'. There's no such thing when playing with mouse and keyboard.

To pause I think you can just press escape, except during a cutscene.