It seems you have already tried almost everything possible. Only a few more things remaining -
Originally Posted by alecbenzer
1) As per your last pastebin on the askubuntu post, you seem to be using kernel 3.8.0-19. Try doing an update to upgrade it to the latest (3.8.0-31) and see if there's any improvement with the newer driver -
2) Try completely disabling IPv6 by editing your /etc/sysctl.conf file.
sudo apt-get update
sudo apt-get dist-upgrade
3) Try adding yet another parameter to your /etc/modprobe.d/iwlwifi.conf file - "bt_coex_active=N"
4) Have you also tried the connection on a Live CD/USB? Sometimes, too much customization also causes negative effects.
sudo sed -i 's/^options.*/& bt_coex_active=N/' /etc/modpeobe.d/iwlwifi.conf
sudo modprobe -rv iwldvm
sudo modprobe -v iwldvm
5) Was the power-management set to "Off" by default on wlan0 (in iwconfig)? The custom script you have in /etc/pm/power.d/wireless, seems to meant for that purpose, but it also disables the default script in /usr/lib/pm-utils/power.d/ directory. So unless it clearly helped it, you should try moving (or removing) that custom script -
After trying these, if there is still speed drop, connection freeze issue, please run the wireless script again, and post back the fresh report here. Along with the report, please also post the output of -
sudo mv /etc/pm/power.d/wireless ~/Desktop
sudo iwpriv wlan0
grep -iR [0-9a-z] /sys/module/iwlwifi/parameters/