About length:

Yes you need to increase the length of your essay. Try to take it up to 19; practice would do it so do not worry much on that; just keep practicing. You will be writing on blank pages there as well and paper size might be A4 or A5. If you write very small then14-15 pages may do that but increase the length. Write as much as you can. I don't say write 30 or 50 pages but 18-19 might make a good read for the examiner.

About Long pauses:

Yeah you cannot afford to pause even for seconds. You'll overcome this issue once you know what you are writing. When you write for A it means you are writing a,b,c and so on. A is just the theme of a,b,c.. you can write all of that in one paragraph. In case it's very long then you may divide in two paragraphs. I write a bit long paragraphs mostly. Some people even make very small paragraphs of 2 or 3 lines even. I don't encourage this way of writing.

I hope that I'll be able to write Essay on Terrorism by tomorrow then you may figure out from there how I would have written that. The point I wanted to make about moving from one paragraph to the next would be clear to you that way properly, I suppose.

Till then grab another topic and start writing. Also work for grammar paper as well. These two are the most important papers. After this I consider Islamiat paper that you have to qualify. If you have 20 days. Try to write 10 essays at least. Don't worry I didn't write any essay but one that too in a mock exam before my first attempt. I qualified that one too so don't underestimate yourself. Next time I could afford no risk so I practiced somewhat 4-5 essays. If you write 10-15 essays that will help you not only in your essay but overall you'll be able to write well in your optionals and PA and CA papers. You won't lose anything by writing essays
I may suggest few topics:

Women Empowerment
Energy Crisis
Global Warming
Globalization
Freedom of media
Institutiuon of Justice and Equality
Islam a religion of peace / Islam Vs West/ Fundamental Extremism
Pakistan in International World

I wish you all the best

P.s

Before writing on these topics do little research on them or read 3-4 articles online/ newspapers to get some background knowledge. This way you'll know more dimensions in which you can stike your pen. Also, do not waste a lot of time researching like days; it must be in hours.