0w-30 and 5w-30 are have the same viscosity at operating temperatures. The 0w will flow better during cold starts, leading to less engine wear. In Karachi weather though, the advantage of 0w is neglibible.
As for fuel economy, you will be best off with 5w-20, or 0w-20 if you can find one. 5w-20 is quite shear resistant, with a spread of only 15 between hot and cold viscosities. If you are uncomfortable with SAE 20 oil, you can go up to SAE 30 oil (0w-30 or 5w-30). You will barely note the difference; a 20 weight oil behaves quite similarly to a 30 weight oil. Whatever you choose, you should regularly check the oil level on the dipstick; don't let it fall below the min mark, or go above the max mark. Both will damage the engine.
As for the API ratings, this is quite an outdated manual, when advanced grades were not available in Pakistan. You can use any API rating; this car is not particularly picky about the grade, since it lacks a cat con and it has roller rockers. Older grades will not have 0w/5w-20 or 0w/5w-30 though.