Hi!
Thats true, customs at Islamabad can open all your luggage. Its better to take a porter before entering the airport. He will charge you 200 Rs and you need to buy the receipt from counter before entering the airport. Don't pay any tip afterwards. Be polite with custom officials and although they are very rude you should be polite with them and smile. I met a young officer at Islamabad last time when I went to Germany. I talked to him politely and he didn't open my luggage. He just asked what is inside the suit case. I had some medicines in my bag and he asked if I am carrying any medicine. I said yes and he asked for the prescription and I showed him as it was handy. Remember if you are carrying any medicine, carry the prescription and keep it handy to save time.
@ POE in Canada
In addition to documents you stated carry
1) If you will be carrying $10,000 or more per person you will have to declare. Better fill the following form in advance and sign in presence of border official.
http://www.cbsa.gc.ca/publications/forms-formulaires/e677.pdf
also a declaration card will be given to you on PIA flight when you will be near CANADA before landing.
http://www.cbsa-asfc.gc.ca/publications/forms-formulaires/e311-eng.pdf
Keep ball point handy so you can fill this card.You will have to tick yes "I am bringing in to Canada currency/monetary instruments totaling CAD10k or more"
Wish you a safe journey and happy landing....Good luck..