Well, it is hard to judge from consumption if you car has some kind of injection problems.
Yes consumption of 18km/l (or ~5.5l/100km) is reachable with that car, but you must behave yourself and you must avoid city traffic
I usually do between 16 and 17km/l. But if you do a lot of city driving, or high speed motorway driving (over 130kph) then it is normal to have higher consumption.
About correction factors, if your car is JTDm, then the values should be below 0.4mm3/inj. On older cars the limit was 0.9mm3/inj. But from my experience, most cars run above that values without any problems.
If you dont see any smoke at high revs, or if your car idles without too much vibration, then everything is probably OK, if not, then you should get the injectors tested on the flow bench at local Bosch Diesel service center. And cleaned if necessary. If you clean them, then they must be tested again on the flow bench, and you get new correction codes for each injector. Those codes must be programmed to ECU by Fiat Examiner at your local Alfa dealership...