I got 74 in CSS exam ,though that was long time ago and then 78 in pms ,that's quite recently . So maybe I can help with this thing, as per my knowledge and experience.
Prepartition from ikram rabbani and trek to Pakistan. Just read trek to Pakistan once. It will take a week. And then ikram rabbani. There are like less than 30 pages on prepartition in ikram rabbani. So that's not an issue. For prepartition these sources are enough. Hardly there will be any topic remaining.
Then for post partition. Well, it seems like you have decided to do it from Ikram rabbani. Then give it a go. But try to do just those topics which are written in less number of pages. For example if there is a topic on nuclear disarmament and it consists of 15 to 20 pages then fine do it from Ikram rabbani. I skipped political history of Pakistan type portion. And that portion consists of like more than 50 pages in ikram rabbani a book. But if you are interested in doing political history portion then you can do it online. And with it read book :Pakistan A dream gone sour . Small book ,will take 3 days.
Ideology portion is there in ikram rabbani. You can find notes on it in Pakistan affairs section here at this forum.
Remember you have to basically read stuff carefully. And then in second go you can remember the important stuff like dates , names of leaders in different events etc.
You can get these books from old books shops. Ikram rabbani for 200 and trek for like 100 ruppees. And I don't think they are available online.
And yes basically for post partition you have to do the topics from where you think it's comfortable for you. Some people find Wikipedia comfortable. So be it Wikipedia. But try to add some quotes ,quotes from newspapers ,editorials etc and then try to add maps too ,where needed.
Best of luck.

__________________
''Sufficient for us is Allah , and He is the best Disposer of affairs" Al-Quran