1) If you go to the Foreign Policy window and then to the Minor Races, you'll see a statement something like this:
If we plan to properly wage war against them, it'd be wise to allocate money towards espionage.
As far as I can tell there's no way to spy on Minors. Is this a bug or a feature that's not yet in the game?
2) After you achieve advanced levels of espionage on a major, the Reports tab of the Foreign Policy screen says something like "No further espionage spending is needed ... we know everything there is to know about the XXX empire". If you cut off espionage spending at that point, do you still have the ability to steal techs?