So, I'm wondering how the Empire or anyone else maintains control of space, given the realities of Hyperspace...
Are ships in Hyperspace detectable?
Are they interceptable (short of having a deployable sun)?
and given as any ship with a Hyperspace drive can simply jump, how do pursuits work?
I'd recommend looking on Wookieepedia for the details on hyperspace, but to answer your questions more generally:
Ships in hyperspace can't be detected, but hyperspace signatures can, so you can see where a ship has jumped and try to guess where it's jumped too (this is why, when trying to escape, ships will often plot a short jump, drop out of hyperspace, then make another jump or series of jumps before heading toward their real destination).
There are also Interdictor ships that the Empire (and other entities) use to pull ships out of hyperspace; basically, it creates a giant mass shadow to force a ship's failsafes to kick in and drop out of hyperspace--basically tricking the ship into thinking it's going to hit a sun or something so that it forces a stop.
Ships in hyperspace can be detected. You see it in Return of the Jedi