Replace light switch with weird wiring and no ground
I agree, the /3 Romex is certainly intentional future-proofing in case you add a ceiling fan later.  Unused wires should be capped, not wired to hot.  

It looks like the Romex they used does indeed have a ground wire in it, and they have grounded the steel junction boxes, assuming corrosion has not damaged that. 

However, note how the yokes (metal ears) of the switch and receptacle attach to the metal boxes, i.e. Only by the screws.  The yoke does not bottom out onto the metal box, and where it makes contact is painted.  The screw threads are not a legitimate grounding path.  

So.   Buy a couple feet of 12/2 NM cable and tear off the sheath and grab the ground wire.  If you need more ground wire, strip the insulation off the other wires.  Cut about a 6" length and pigtail it off the ground screw of the switch or receptacle.  Then, unhook the ground wire(s) screwed onto the back of the box, and replace that with about a 6-8" pigtail.   Now join both pigtails, plus the wire(s) you took off the screw, with a wire nut (red or green should be the best size). Shove all that into the back of the box.   

Are those ground wires any good?  The simple way is to use a 3-lamp tester and look for 2 yellow lights, or measure 120V between hot and ground.  

The more conclusive way is to deliberately connect a duplex receptacle so the hot and neutral screws are actually connected to hot and ground wires.  Then hook up a big load like a hair dryer or 1500W heater, measure the voltage across hot to ground, turn on the load momentarily, and measure the voltage again.  Don't leave it on.  It should sag only a few volts, about the same as it sags when wired correctly.  Ground is not neutral and is not a substitute for neutral, but it is intentionally bonded at the panel, and this tests that continuity under load. 

Almost any test between hot and ground will trip a GFCI device, since it is in fact a ground fault.