One piece of junk that you sent me as a sample. Sorry to be rude but that is not a covering letter but a short novel with complex minute details.
I stopped reading in the middle because I was gasping for breath. Follow kiss method suggested by Umair. It sounded like you were hell bent on trying to convince visa officer for your return to your lovely country Pakistan. Visa officer will still review your all docs through a methodical system implemented by them. Good luck.
It is just my opinion. Everyone is a free soul. They can use their own mind.