Greetings from Islamabad,
There are plenty of air carriers that make to Islamabad from KL, likewise Thai airway, Etihad, Saudi Airlines, PIA etc. so please check the deals , sometimes they offer very reasonable fares.
Good luck ..
My favourite search app is Skyscanner.
You should book 30-40 days before your travel. You'd get the same fare as you get now. Your own airline is perfect.
Sometimes the airlines offer some good deals a few months earlier and those are much cheaper.