Shepard may live, if you have enough war assets and choose the destroy option.
Most of the people you listed die. However, faster-than-light travel is possible in the ME3 universe, also without Mass Effect relays, so space travel won't be impossible, just highly inconvenient (bizarrely, communication might still be possible, as we have instantaneous, galaxy-wide communication). Also, there is a certain logic to destroying the Mass Effect relays. They were reaper/godchild constructions anyway, so cleansing the galaxy of one should probably remove the other too (not necessarily from a technical, but from a dramatical/storytelling perspective).
The prize you get is billions and billions of survivors on the planets attacked by reapers - not least Earth, which was the major objective for this instalment of the series. I agree the ending is bittersweet, and I'd probably have preferred a more "uplifting" end, but I guess galactic salvation doesn't come cheap.
Don't get me started on the Normandy escape/magic LI survival, though...