The same sort of incident had happened with me in my first attempt of css. I scored better but i failed in Islamiat and that too by scoring just 30 marks. Actually by 2010 people never used to fail in Islamiat and that's why the aspirants never took it that serious . I passed English Essay with 40 while English Precise and Composition with good 71 marks. but Islamiat proved to be a nightmare for me. however, afterwards I took it as a challenge and in the next attempts I was able to score 59 and 68. Thats' why you need not to be disheartened and should take this overall impressive result as morale booster and should focus on Islamiat. With little concentration and extra effort , you may score impressive in it.
I brought the following changes in my strategy after the failure in Islamiat.

The very first thing , i took it as a challenge.
Secondly, I changed the medium from Urdu to English as my Urdu handwriting was pathetic and Urdu handwriting speed was slowest which could not help me write answers of five questions..
Thirdly, I found Ayat e Quran and Ahadith related to various important topics and memorized those in their Arabic without memorizing their translation. I used to create a context while answering , and would quote the Ayat e Quran in their arabic with marker . For instance while I was answering a question regarding women rights in Islam and i had to elaborate my point by describing women's right in inheritance I wrote that Islam has stressed on providing women their share in inheritence as Allah has ordained in Quran ,
"لِّلرِّجَالِ نَصيِبٌ مِّمَّا تَرَكَ الْوَالِدَانِ وَ الأَقْرَبُونَ وَ لِلنِّسَاء نَصِيبٌ مِّمَّا تَرَكَ الْوَالِدَانِ وَ الأَقْرَبُونَ مِمَّا قَلَّ مِنْهُ أَوْ كَثُرَ نَصِيبًا مَّفْرُوضًا" Now I didnt quote the translation and left it to examiner to judge whether the Ayat is in accordance with the context and proves my point or not. And I was able to obtain 68 marks when many other aspirants still failed in Islamiat.
I also showed obsession towards reading various books. Prof Arshad Chadhar's book by JWT was one of them. It provided my with good number of Ayats and Ahadith as well as some good concepts. I used to read a topic from 4 to 5 books and would understand the crux of all of them and would note down the main points.
Another thing which i did was , I prepared objective portion of this paper with an obsession. For this i solved past 15 years css Islamiat papers objective and also solved last 5 exas' PMS past papers Islamiat Objective. Moreover, importantly , I obtained Prof. Zaka sahb 's 1000 point Islamiat Objectice notes which proved highly instrumental in helping strengthen my objective part preparation.

Thats how , I was able to score 68. Had I been possessed with speedy handwriting , i would have crossed 70 . Believe me , memorizing Ayat e Qurani is far far far far easier then memorizing their translation and the impact the original ayat create on examiner is far strong then that created by the translation.
Moreover, one may quote poetic verses also. Like in one of the question the examiner asked thge difference between jihad and Fitna and i started the question with the following poetic verse.
Na Haq Kay Liay Uthay Tu Shamshir Bhi Fitna
Shamshir Kya , Naara e Takbir Bhi Fitnah
I felt if i were examiner , I would definitely had been impressed.

This is the method which really worked for me.

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Thanks Allah