From one first-timer to another
I appreciate what yr doing; I'm doing it myself too. Kudos to ambition. That being said, you need to get some good books on plumbing code before you go any further.
To me, venting was the most difficult thing to grasp. I would originally have thought what you think, but I've been given advice from experts (namely, HJ and Gary) and have read everywhere that every single fixture needs to be individually vented. If you don't do this, there are many reasons why the shower trap may fail to work properly. In your proposed configuration, I'd speculate that the toilet draining past the shower branch could pull water out of the trap, or that if the shower is far enough from the drain, draining water from the shower could siphon out its trap.
I assume you'll build a wall between the shower and the drain, so that'd be a convenient place to put the shower vent. That vent line can join the sink or toilet or main vent line along the ceiling of the basement. You don't have to run a separate, dedicated vent out the roof - just a separate branch to the fixture.
Also, I defer to Gary's experience with a hammer drill, but for what it's worth, I used an SDSMax rotary hammer which is a quite a bit more powerful than a hammer drill, and it still took reasonable effort to drill and chip out a sump hole. I drilled 1/2" holes on the perimeter of the hole and chipped out the center. I will say, though that it made for a neat job, and was virtually dust free. I think, though, in the end it's worth the extra $ and clean up to saw and chip with a larger hammer. The less stress you can put on your back, the better (IMHO).
BTW, where's the toilet vent? Am I missing something?
PS: I'm jealous your main drain exits the house below the slab! I have to use a pump.