Cultus is a good car, you wont have any problems in it... You can come nonstop without resting your car...
You will make tea/fuel/food right? Cultus will rest on those stops 
About Sindh, I always travel at night and its safe..... If you have issues traveling at night then why dont to stop in Sadiqabad for night stay, Midway hotel on N5 is best option, about 5k per night... From Sadiqabad it will take around 10 hours with few stops on the way.
Any problems with the car on the road, call 130, help will be there in 15 minutes 