All the IPs in the range will share the bandwidth of 200Kbps for the rules you set up. You can get more details about the bandwidth control setup in this link: http://www.tp-link.com/us/faq-557.html

The remote management occupied port 80 by default. You may try to change the port of remote management under Security-->Remote Management to another one, then try to open port.

Is the slow speed with wired connection, or wireless connection? If the slow speed is for wired connection, then normally we can just upgrade firmware and reset. For C3200 2.4G issue, you may check...

May I know which firmware you are trying to upgrade? Since you are from UK, you may go to the UK website to get the corresponding firmware : http://uk.tp-link.com/download/Archer-D2.html#Firmware And...

You may refer to this link to set up your internet: http://www.tp-link.com.au/faq-541.html

As I know, the special characters is not supported for PPP username and password. You may check whether your internet service provider can change the username and password on their side to be numbers...