Fuel mileage is correct for the year.
Battery could be a bunch of things.  One check that the glove box light is
not staying on.
use an amp probe check for amp pull with key off, and disconnect the voltage
regulator and see if it goes away. 2.3 was a tuff engine, not a power house
for its day, but few mechanical issues.  Timing belts easy to replace, Ford
says every 60K.  If its a standard 2.3 and not the so called "high output"
its not a crasher, few trucks got the high output.  crasher means if timing
belt breaks piston will hit valves.  rear brakes undersized, so are the
fronts. Hydraulic clutch can be a problem, slave is in side bell housing and
if it leaks fluid messes up clutch disk.

Whitelightning

I had one, now I have the third Ranger.  But my 83 got around
24 highway and 18 city.  I had a manual trans. Maybe you got
a low rear end?

The alternator sometimes have a diode go bad and it lets the
battery drain.  You would have to be good at electronics to find
it and it doesn't test this when you check it at Autozone, I think.

Put plugs and wires and such, if it runs pretty good don't rebuild
the carb, I never had that help mileage.

Ouch. With a new set of plugs (fouled by a tank of bad gas), an intake
induction cleaning and a recharge of my K&B high flow air filter all at
34,000 miles my 2003 2WD F150 with the 4.2L V-6 is getting 14.5 mpg city
and 18=19 highway (if I observe the speed limit).

Good luck with the battery drain issue. That can be one of those things
that drives one to drink.